[PATCH v2 0/6] alloc_tag: introduce IOCTL-based filtering for MAP

[PATCH v2 0/6] alloc_tag: introduce IOCTL-based filtering for MAP

[Abhishek Bapat]

Currently, memory allocation profiling data is primarily exposed through
/proc/allocinfo. While useful for manual inspection, this text-based
interface poses challenges for production monitoring and large-scale
analysis:

1. Userspace must parse large amounts of text to extract specific
fields.
2. To find specific tags, userspace must read the entire dataset,
requiring many context switches and high data copying.
3. The kernel currently aggregates per-CPU counters for every allocation
size, even those the user intends to filter out immediately.

This series introduces a new IOCTL-based binary interface for allocinfo
that supports kernel-side filtering. By allowing the user to specify a
filter mask, we significantly reduce the work performed in-kernel and
the amount of data transferred to userspace.

Performance measurements were conducted on an Intel Xeon Platinum 8481C
(224 CPUs) with caches dropped before each run.

The IOCTL mechanism shows a ~20x performance improvement for
filtered queries. The kernel avoids the expensive per-CPU counter
aggregation (alloc_tag_read) for any tags that fail the initial string
or location filters.

Scenario 1: Specific File Filtering (arch/x86/events/rapl.c)
1. Traditional (cat /proc/allocinfo | grep): 22ms (sys)
2. IOCTL Interface: 1ms (sys)

Scenario 2: Compound Filtering (Filename + Size)
1. Traditional: (cat ... | grep | awk): 21ms (sys)
2. IOCTL Interface: 1ms (sys)

Scenario 3: Size-Based Filtering (min_size = 1MB)
1. Traditional: (cat ... | awk): 21ms (sys)
2. IOCTL Interface: 14ms (sys)

v2 changes:
- Patch 1/6: Introduced locking for m->private. Also included the new uapi
header file in MAINTAINERS list.
- Patch 2/6: Handled the case where ALLOCINFO_FILTER_MASK_MODNAME is
passed but ct->modname is NULL.
- Patch 3/6: Moved min_size and max_size outside of struct allocinfo_tag
into struct allocinfo_filter. Added validation that min_size <=
max_size. Prefetched alloc_tag_counters if size based filter masks are
provided to avoid assimilating per-cpu counters twice.
- Patch 5/6: Removed the hardcoded logic to skip the header, instead the
test will skip lines that don't match the format. Also included the
newly added alloc_tag selftests directory in MAINTAINERS list.

Abhishek Bapat (5):
  alloc_tag: add ioctl filters to /proc/allocinfo
  alloc_tag: add size-based filtering to ioctl
  alloc_tag: add accuracy based filtering to ioctl
  kselftest: alloc_tag: add kselftest for ioctl interface
  kselftest: alloc_tag: extend the allocinfo ioctl kselftest

Suren Baghdasaryan (1):
  alloc_tag: add ioctl to /proc/allocinfo

 .../userspace-api/ioctl/ioctl-number.rst      |   2 +
 MAINTAINERS                                   |   2 +
 include/linux/codetag.h                       |   1 +
 include/uapi/linux/alloc_tag.h                |  87 +++
 lib/alloc_tag.c                               | 303 ++++++++++-
 lib/codetag.c                                 |  11 +
 tools/testing/selftests/alloc_tag/Makefile    |   9 +
 .../alloc_tag/allocinfo_ioctl_test.c          | 505 ++++++++++++++++++
 8 files changed, 918 insertions(+), 2 deletions(-)
 create mode 100644 include/uapi/linux/alloc_tag.h
 create mode 100644 tools/testing/selftests/alloc_tag/Makefile
 create mode 100644 tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c

-- 
2.54.0.746.g67dd491aae-goog

[PATCH v2 1/6] alloc_tag: add ioctl to /proc/allocinfo

[Abhishek Bapat]

From: Suren Baghdasaryan <surenb@google.com>

Add the following ioctl commands for /proc/allocinfo file:

ALLOCINFO_IOC_CONTENT_ID - gets content identifier which can be used
to check whether the file content has changed specifically due to module
load/unload. Every time a module is loaded / unloaded, the returned
value will be different. By comparing the identifier value at the
beginning and at the end of the content retrieval operation, users can
validate retrieved information for consistency.

ALLOCINFO_IOC_GET_AT - gets the record at the specified position. This
is the position of a record in /proc/allocinfo.

ALLOCINFO_IOC_GET_NEXT - gets the record next to the last retrieved
one. If no records were previously retrieved, returns the first
record.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Abhishek Bapat <abhishekbapat@google.com>
---
 .../userspace-api/ioctl/ioctl-number.rst      |   2 +
 MAINTAINERS                                   |   1 +
 include/linux/codetag.h                       |   1 +
 include/uapi/linux/alloc_tag.h                |  54 +++++
 lib/alloc_tag.c                               | 193 +++++++++++++++++-
 lib/codetag.c                                 |  11 +
 6 files changed, 260 insertions(+), 2 deletions(-)
 create mode 100644 include/uapi/linux/alloc_tag.h

diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 331223761fff..84f6808a8578 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -349,6 +349,8 @@ Code  Seq#    Include File                                             Comments
                                                                        <mailto:luzmaximilian@gmail.com>
 0xA5  20-2F  linux/surface_aggregator/dtx.h                            Microsoft Surface DTX driver
                                                                        <mailto:luzmaximilian@gmail.com>
+0xA6  00-0F  uapi/linux/alloc_tag.h                                    Memory allocation profiling
+                                                                       <mailto:surenb@google.com>
 0xAA  00-3F  linux/uapi/linux/userfaultfd.h
 0xAB  00-1F  linux/nbd.h
 0xAC  00-1F  linux/raw.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 46ed0f0e76d8..d176bde8fbfc 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16709,6 +16709,7 @@ S:	Maintained
 F:	Documentation/mm/allocation-profiling.rst
 F:	include/linux/alloc_tag.h
 F:	include/linux/pgalloc_tag.h
+F:	include/uapi/linux/alloc_tag.h
 F:	lib/alloc_tag.c
 
 MEMORY CONTROLLER DRIVERS
diff --git a/include/linux/codetag.h b/include/linux/codetag.h
index 8ea2a5f7c98a..2bcd4e7c809e 100644
--- a/include/linux/codetag.h
+++ b/include/linux/codetag.h
@@ -76,6 +76,7 @@ struct codetag_iterator {
 
 void codetag_lock_module_list(struct codetag_type *cttype, bool lock);
 bool codetag_trylock_module_list(struct codetag_type *cttype);
+unsigned long codetag_get_content_id(struct codetag_type *cttype);
 struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype);
 struct codetag *codetag_next_ct(struct codetag_iterator *iter);
 
diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h
new file mode 100644
index 000000000000..e9a5b55fcc7a
--- /dev/null
+++ b/include/uapi/linux/alloc_tag.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ *  include/linux/alloc_tag.h
+ */
+
+#ifndef _UAPI_ALLOC_TAG_H
+#define _UAPI_ALLOC_TAG_H
+
+#include <linux/types.h>
+
+#define ALLOCINFO_STR_SIZE	64
+
+struct allocinfo_content_id {
+	__u64 id;
+};
+
+struct allocinfo_tag {
+	/* Longer names are trimmed */
+	char modname[ALLOCINFO_STR_SIZE];
+	char function[ALLOCINFO_STR_SIZE];
+	char filename[ALLOCINFO_STR_SIZE];
+	__u64 lineno;
+};
+
+struct allocinfo_counter {
+	__u64 bytes;
+	__u64 calls;
+	__u8 accurate;
+	__u8 pad[7]; /* Add alignment to not break the 32-bit compatible interface */
+};
+
+struct allocinfo_tag_data {
+	struct allocinfo_tag tag;
+	struct allocinfo_counter counter;
+};
+
+struct allocinfo_get_at {
+	__u64 pos;	/* input */
+	struct allocinfo_tag_data data;
+};
+
+#define _ALLOCINFO_IOC_CONTENT_ID	0
+#define _ALLOCINFO_IOC_GET_AT		1
+#define _ALLOCINFO_IOC_GET_NEXT		2
+
+#define ALLOCINFO_IOC_BASE		0xA6
+#define ALLOCINFO_IOC_CONTENT_ID	_IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_CONTENT_ID,	\
+					     struct allocinfo_content_id)
+#define ALLOCINFO_IOC_GET_AT		_IOWR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_AT,	\
+					      struct allocinfo_get_at)
+#define ALLOCINFO_IOC_GET_NEXT		_IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_NEXT,	\
+					     struct allocinfo_tag_data)
+
+#endif /* _UAPI_ALLOC_TAG_H */
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index b9ca95d1f506..3598735b6c93 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -5,6 +5,7 @@
 #include <linux/gfp.h>
 #include <linux/kallsyms.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/page_ext.h>
 #include <linux/pgalloc_tag.h>
 #include <linux/proc_fs.h>
@@ -14,6 +15,7 @@
 #include <linux/string_choices.h>
 #include <linux/vmalloc.h>
 #include <linux/kmemleak.h>
+#include <uapi/linux/alloc_tag.h>
 
 #define ALLOCINFO_FILE_NAME		"allocinfo"
 #define MODULE_ALLOC_TAG_VMAP_SIZE	(100000UL * sizeof(struct alloc_tag))
@@ -46,6 +48,10 @@ int alloc_tag_ref_offs;
 struct allocinfo_private {
 	struct codetag_iterator iter;
 	bool print_header;
+	/* ioctl uses a separate iterator not to interfere with reads */
+	struct codetag_iterator ioctl_iter;
+	bool positioned; /* seq_open_private() sets to 0 */
+	struct mutex ioctl_lock;
 };
 
 static void *allocinfo_start(struct seq_file *m, loff_t *pos)
@@ -125,6 +131,190 @@ static const struct seq_operations allocinfo_seq_op = {
 	.show	= allocinfo_show,
 };
 
+static int allocinfo_open(struct inode *inode, struct file *file)
+{
+	int ret;
+
+	ret = seq_open_private(file, &allocinfo_seq_op,
+			       sizeof(struct allocinfo_private));
+	if (!ret) {
+		struct seq_file *m = file->private_data;
+		struct allocinfo_private *priv = m->private;
+
+		mutex_init(&priv->ioctl_lock);
+	}
+	return ret;
+}
+
+static int allocinfo_release(struct inode *inode, struct file *file)
+{
+	return seq_release_private(inode, file);
+}
+
+static const char *allocinfo_str(const char *str)
+{
+	size_t len = strlen(str);
+
+	/* Keep an extra space for the trailing NULL. */
+	if (len >= ALLOCINFO_STR_SIZE)
+		str += (len - ALLOCINFO_STR_SIZE) + 1;
+	return str;
+}
+
+/* Copy a string and trim from the beginning if it's too long */
+static void allocinfo_copy_str(char *dest, const char *src)
+{
+	strscpy(dest, allocinfo_str(src), ALLOCINFO_STR_SIZE);
+}
+
+static void allocinfo_to_params(struct codetag *ct,
+				struct allocinfo_tag_data *data)
+{
+	struct alloc_tag *tag = ct_to_alloc_tag(ct);
+	struct alloc_tag_counters counter = alloc_tag_read(tag);
+
+	if (ct->modname)
+		allocinfo_copy_str(data->tag.modname, ct->modname);
+	else
+		data->tag.modname[0] = '\0';
+	allocinfo_copy_str(data->tag.function, ct->function);
+	allocinfo_copy_str(data->tag.filename, ct->filename);
+	data->tag.lineno = ct->lineno;
+	data->counter.bytes = counter.bytes;
+	data->counter.calls = counter.calls;
+	data->counter.accurate = !alloc_tag_is_inaccurate(tag);
+}
+
+static int allocinfo_ioctl_get_content_id(struct seq_file *m, void __user *arg)
+{
+	struct allocinfo_content_id params;
+
+	codetag_lock_module_list(alloc_tag_cttype, true);
+	params.id = codetag_get_content_id(alloc_tag_cttype);
+	codetag_lock_module_list(alloc_tag_cttype, false);
+	if (copy_to_user(arg, &params, sizeof(params)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg)
+{
+	struct allocinfo_private *priv;
+	struct codetag *ct;
+	__u64 pos;
+	struct allocinfo_get_at params = {0};
+
+	if (copy_from_user(&params, arg, sizeof(params)))
+		return -EFAULT;
+
+	priv = (struct allocinfo_private *)m->private;
+	pos = params.pos;
+
+	mutex_lock(&priv->ioctl_lock);
+	codetag_lock_module_list(alloc_tag_cttype, true);
+
+	/* Find the codetag */
+	priv->ioctl_iter = codetag_get_ct_iter(alloc_tag_cttype);
+	ct = codetag_next_ct(&priv->ioctl_iter);
+	while (ct && pos--)
+		ct = codetag_next_ct(&priv->ioctl_iter);
+	if (ct) {
+		allocinfo_to_params(ct, &params.data);
+		priv->positioned = true;
+	}
+
+	codetag_lock_module_list(alloc_tag_cttype, false);
+	mutex_unlock(&priv->ioctl_lock);
+
+	if (!ct)
+		return -ENOENT;
+
+	if (copy_to_user(arg, &params, sizeof(params)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int allocinfo_ioctl_get_next(struct seq_file *m, void __user *arg)
+{
+	struct allocinfo_private *priv;
+	struct codetag *ct;
+	struct allocinfo_tag_data params = {0};
+	int ret = 0;
+
+	priv = (struct allocinfo_private *)m->private;
+
+	mutex_lock(&priv->ioctl_lock);
+	codetag_lock_module_list(alloc_tag_cttype, true);
+
+	if (!priv->positioned) {
+		priv->ioctl_iter = codetag_get_ct_iter(alloc_tag_cttype);
+		priv->positioned = true;
+	}
+
+	ct = codetag_next_ct(&priv->ioctl_iter);
+	if (ct)
+		allocinfo_to_params(ct, &params);
+
+	if (!ct) {
+		priv->positioned = false;
+		ret = -ENOENT;
+	}
+	codetag_lock_module_list(alloc_tag_cttype, false);
+	mutex_unlock(&priv->ioctl_lock);
+
+	if (ret == 0) {
+		if (copy_to_user(arg, &params, sizeof(params)))
+			return -EFAULT;
+	}
+	return ret;
+}
+
+static long allocinfo_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long __arg)
+{
+	void __user *arg = (void __user *)__arg;
+	int ret;
+
+	switch (cmd) {
+	case ALLOCINFO_IOC_CONTENT_ID:
+		ret = allocinfo_ioctl_get_content_id(file->private_data, arg);
+		break;
+	case ALLOCINFO_IOC_GET_AT:
+		ret = allocinfo_ioctl_get_at(file->private_data, arg);
+		break;
+	case ALLOCINFO_IOC_GET_NEXT:
+		ret = allocinfo_ioctl_get_next(file->private_data, arg);
+		break;
+	default:
+		ret = -ENOIOCTLCMD;
+		break;
+	}
+
+	return ret;
+}
+
+#ifdef CONFIG_COMPAT
+static long allocinfo_compat_ioctl(struct file *file, unsigned int cmd,
+				   unsigned long arg)
+{
+	return allocinfo_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+static const struct proc_ops allocinfo_proc_ops = {
+	.proc_open		= allocinfo_open,
+	.proc_read_iter		= seq_read_iter,
+	.proc_lseek		= seq_lseek,
+	.proc_release		= allocinfo_release,
+	.proc_ioctl		= allocinfo_ioctl,
+#ifdef CONFIG_COMPAT
+	.proc_compat_ioctl	= allocinfo_compat_ioctl,
+#endif
+
+};
+
 size_t alloc_tag_top_users(struct codetag_bytes *tags, size_t count, bool can_sleep)
 {
 	struct codetag_iterator iter;
@@ -989,8 +1179,7 @@ static int __init alloc_tag_init(void)
 		return 0;
 	}
 
-	if (!proc_create_seq_private(ALLOCINFO_FILE_NAME, 0400, NULL, &allocinfo_seq_op,
-				     sizeof(struct allocinfo_private), NULL)) {
+	if (!proc_create(ALLOCINFO_FILE_NAME, 0400, NULL, &allocinfo_proc_ops)) {
 		pr_err("Failed to create %s file\n", ALLOCINFO_FILE_NAME);
 		shutdown_mem_profiling(false);
 		return -ENOMEM;
diff --git a/lib/codetag.c b/lib/codetag.c
index 304667897ad4..93aa30991563 100644
--- a/lib/codetag.c
+++ b/lib/codetag.c
@@ -48,6 +48,17 @@ bool codetag_trylock_module_list(struct codetag_type *cttype)
 	return down_read_trylock(&cttype->mod_lock) != 0;
 }
 
+unsigned long codetag_get_content_id(struct codetag_type *cttype)
+{
+	lockdep_assert_held(&cttype->mod_lock);
+
+	/*
+	 * next_mod_seq is updated on every load, so can be used to identify
+	 * content changes.
+	 */
+	return cttype->next_mod_seq;
+}
+
 struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype)
 {
 	struct codetag_iterator iter = {
-- 
2.54.0.746.g67dd491aae-goog

[PATCH v2 2/6] alloc_tag: add ioctl filters to /proc/allocinfo

[Abhishek Bapat]

Extend the capability of the IOCTL mechanism to filter allocations based
on tag's module name, function name, file name and line number.

Signed-off-by: Abhishek Bapat <abhishekbapat@google.com>
---
 include/uapi/linux/alloc_tag.h | 26 ++++++++++++++-
 lib/alloc_tag.c                | 58 ++++++++++++++++++++++++++++++++--
 2 files changed, 80 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h
index e9a5b55fcc7a..0cc9db5298c6 100644
--- a/include/uapi/linux/alloc_tag.h
+++ b/include/uapi/linux/alloc_tag.h
@@ -34,8 +34,32 @@ struct allocinfo_tag_data {
 	struct allocinfo_counter counter;
 };
 
+enum {
+	ALLOCINFO_FILTER_MODNAME,
+	ALLOCINFO_FILTER_FUNCTION,
+	ALLOCINFO_FILTER_FILENAME,
+	ALLOCINFO_FILTER_LINENO,
+	__ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_LINENO
+};
+
+#define ALLOCINFO_FILTER_MASK_MODNAME		(1 << ALLOCINFO_FILTER_MODNAME)
+#define ALLOCINFO_FILTER_MASK_FUNCTION		(1 << ALLOCINFO_FILTER_FUNCTION)
+#define ALLOCINFO_FILTER_MASK_FILENAME		(1 << ALLOCINFO_FILTER_FILENAME)
+#define ALLOCINFO_FILTER_MASK_LINENO		(1 << ALLOCINFO_FILTER_LINENO)
+
+#define ALLOCINFO_FILTER_MASKS \
+	((1 << (__ALLOCINFO_FILTER_LAST + 1)) - 1)
+
+struct allocinfo_filter {
+	__u64 mask; /* bitmask of the filter fields used */
+	struct allocinfo_tag fields;
+};
+
 struct allocinfo_get_at {
-	__u64 pos;	/* input */
+	/* inputs */
+	__u64 pos;
+	struct allocinfo_filter filter;
+	/* output */
 	struct allocinfo_tag_data data;
 };
 
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 3598735b6c93..56c394ef721f 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -48,6 +48,7 @@ int alloc_tag_ref_offs;
 struct allocinfo_private {
 	struct codetag_iterator iter;
 	bool print_header;
+	struct allocinfo_filter filter;
 	/* ioctl uses a separate iterator not to interfere with reads */
 	struct codetag_iterator ioctl_iter;
 	bool positioned; /* seq_open_private() sets to 0 */
@@ -167,6 +168,11 @@ static void allocinfo_copy_str(char *dest, const char *src)
 	strscpy(dest, allocinfo_str(src), ALLOCINFO_STR_SIZE);
 }
 
+static int allocinfo_cmp_str(const char *str, const char *template)
+{
+	return strncmp(allocinfo_str(str), template, ALLOCINFO_STR_SIZE);
+}
+
 static void allocinfo_to_params(struct codetag *ct,
 				struct allocinfo_tag_data *data)
 {
@@ -198,27 +204,71 @@ static int allocinfo_ioctl_get_content_id(struct seq_file *m, void __user *arg)
 	return 0;
 }
 
+static bool matches_filter(struct codetag *ct, struct allocinfo_filter *filter)
+{
+	if (!filter || !filter->mask)
+		return true;
+
+	if (filter->mask & ALLOCINFO_FILTER_MASK_MODNAME) {
+		if (!ct->modname)
+			return false;
+		if (allocinfo_cmp_str(ct->modname, filter->fields.modname))
+			return false;
+	}
+
+	if ((filter->mask & ALLOCINFO_FILTER_MASK_FUNCTION) &&
+	    ct->function && (allocinfo_cmp_str(ct->function, filter->fields.function)))
+		return false;
+
+	if ((filter->mask & ALLOCINFO_FILTER_MASK_FILENAME) &&
+	    ct->filename && (allocinfo_cmp_str(ct->filename, filter->fields.filename)))
+		return false;
+
+	if ((filter->mask & ALLOCINFO_FILTER_MASK_LINENO) &&
+	    ct->lineno != filter->fields.lineno)
+		return false;
+
+	return true;
+}
+
 static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg)
 {
 	struct allocinfo_private *priv;
 	struct codetag *ct;
-	__u64 pos;
 	struct allocinfo_get_at params = {0};
+	__u64 skip_count;
 
 	if (copy_from_user(&params, arg, sizeof(params)))
 		return -EFAULT;
 
+	if (params.filter.mask & ~ALLOCINFO_FILTER_MASKS)
+		return -EINVAL;
+
 	priv = (struct allocinfo_private *)m->private;
-	pos = params.pos;
+
+	skip_count = params.pos;
 
 	mutex_lock(&priv->ioctl_lock);
 	codetag_lock_module_list(alloc_tag_cttype, true);
 
+	if (params.filter.mask)
+		priv->filter = params.filter;
+	else
+		priv->filter.mask = 0;
+
 	/* Find the codetag */
 	priv->ioctl_iter = codetag_get_ct_iter(alloc_tag_cttype);
 	ct = codetag_next_ct(&priv->ioctl_iter);
-	while (ct && pos--)
+
+	while (ct) {
+		if (matches_filter(ct, &priv->filter)) {
+			if (skip_count == 0)
+				break;
+			skip_count--;
+		}
 		ct = codetag_next_ct(&priv->ioctl_iter);
+	}
+
 	if (ct) {
 		allocinfo_to_params(ct, &params.data);
 		priv->positioned = true;
@@ -254,6 +304,8 @@ static int allocinfo_ioctl_get_next(struct seq_file *m, void __user *arg)
 	}
 
 	ct = codetag_next_ct(&priv->ioctl_iter);
+	while (ct && !matches_filter(ct, &priv->filter))
+		ct = codetag_next_ct(&priv->ioctl_iter);
 	if (ct)
 		allocinfo_to_params(ct, &params);
 
-- 
2.54.0.746.g67dd491aae-goog

[PATCH v2 3/6] alloc_tag: add size-based filtering to ioctl

[Abhishek Bapat]

Extend the allocinfo filtering mechanism to allow users to filter tags
based on the total number of bytes allocated [min_size, max_size]. The
size range is inclusive.

Filtering by size involves retrieving allocinfo per-CPU counters, which
is an expensive operation. Hence, the performance of size-based
filtering will be worse than other filters.

Signed-off-by: Abhishek Bapat <abhishekbapat@google.com>
---
 include/uapi/linux/alloc_tag.h |  8 +++-
 lib/alloc_tag.c                | 72 ++++++++++++++++++++++++++++------
 2 files changed, 68 insertions(+), 12 deletions(-)

diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h
index 0cc9db5298c6..45f158bee0a6 100644
--- a/include/uapi/linux/alloc_tag.h
+++ b/include/uapi/linux/alloc_tag.h
@@ -39,13 +39,17 @@ enum {
 	ALLOCINFO_FILTER_FUNCTION,
 	ALLOCINFO_FILTER_FILENAME,
 	ALLOCINFO_FILTER_LINENO,
-	__ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_LINENO
+	ALLOCINFO_FILTER_MIN_SIZE,
+	ALLOCINFO_FILTER_MAX_SIZE,
+	__ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_MAX_SIZE
 };
 
 #define ALLOCINFO_FILTER_MASK_MODNAME		(1 << ALLOCINFO_FILTER_MODNAME)
 #define ALLOCINFO_FILTER_MASK_FUNCTION		(1 << ALLOCINFO_FILTER_FUNCTION)
 #define ALLOCINFO_FILTER_MASK_FILENAME		(1 << ALLOCINFO_FILTER_FILENAME)
 #define ALLOCINFO_FILTER_MASK_LINENO		(1 << ALLOCINFO_FILTER_LINENO)
+#define ALLOCINFO_FILTER_MASK_MIN_SIZE		(1 << ALLOCINFO_FILTER_MIN_SIZE)
+#define ALLOCINFO_FILTER_MASK_MAX_SIZE		(1 << ALLOCINFO_FILTER_MAX_SIZE)
 
 #define ALLOCINFO_FILTER_MASKS \
 	((1 << (__ALLOCINFO_FILTER_LAST + 1)) - 1)
@@ -53,6 +57,8 @@ enum {
 struct allocinfo_filter {
 	__u64 mask; /* bitmask of the filter fields used */
 	struct allocinfo_tag fields;
+	__u64 min_size;
+	__u64 max_size;
 };
 
 struct allocinfo_get_at {
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 56c394ef721f..6c8743eead2d 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -173,11 +173,21 @@ static int allocinfo_cmp_str(const char *str, const char *template)
 	return strncmp(allocinfo_str(str), template, ALLOCINFO_STR_SIZE);
 }
 
+static inline struct alloc_tag_counters allocinfo_prefetch_counters(struct codetag *ct)
+{
+	return alloc_tag_read(ct_to_alloc_tag(ct));
+}
+
 static void allocinfo_to_params(struct codetag *ct,
-				struct allocinfo_tag_data *data)
+				struct allocinfo_tag_data *data,
+				struct alloc_tag_counters *counters)
 {
-	struct alloc_tag *tag = ct_to_alloc_tag(ct);
-	struct alloc_tag_counters counter = alloc_tag_read(tag);
+	struct alloc_tag_counters local_counters;
+
+	if (!counters) {
+		local_counters = allocinfo_prefetch_counters(ct);
+		counters = &local_counters;
+	}
 
 	if (ct->modname)
 		allocinfo_copy_str(data->tag.modname, ct->modname);
@@ -186,9 +196,9 @@ static void allocinfo_to_params(struct codetag *ct,
 	allocinfo_copy_str(data->tag.function, ct->function);
 	allocinfo_copy_str(data->tag.filename, ct->filename);
 	data->tag.lineno = ct->lineno;
-	data->counter.bytes = counter.bytes;
-	data->counter.calls = counter.calls;
-	data->counter.accurate = !alloc_tag_is_inaccurate(tag);
+	data->counter.bytes = counters->bytes;
+	data->counter.calls = counters->calls;
+	data->counter.accurate = !alloc_tag_is_inaccurate(ct_to_alloc_tag(ct));
 }
 
 static int allocinfo_ioctl_get_content_id(struct seq_file *m, void __user *arg)
@@ -204,7 +214,8 @@ static int allocinfo_ioctl_get_content_id(struct seq_file *m, void __user *arg)
 	return 0;
 }
 
-static bool matches_filter(struct codetag *ct, struct allocinfo_filter *filter)
+static bool matches_filter(struct codetag *ct, struct allocinfo_filter *filter,
+			   struct alloc_tag_counters *counters)
 {
 	if (!filter || !filter->mask)
 		return true;
@@ -228,6 +239,17 @@ static bool matches_filter(struct codetag *ct, struct allocinfo_filter *filter)
 	    ct->lineno != filter->fields.lineno)
 		return false;
 
+	if ((filter->mask & ALLOCINFO_FILTER_MASK_MIN_SIZE) ||
+	    (filter->mask & ALLOCINFO_FILTER_MASK_MAX_SIZE)) {
+		/* We assume counters is not NULL here as per caller logic */
+		if ((filter->mask & ALLOCINFO_FILTER_MASK_MIN_SIZE) &&
+		    counters->bytes < filter->min_size)
+			return false;
+		if ((filter->mask & ALLOCINFO_FILTER_MASK_MAX_SIZE) &&
+		    counters->bytes > filter->max_size)
+			return false;
+	}
+
 	return true;
 }
 
@@ -237,6 +259,9 @@ static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg)
 	struct codetag *ct;
 	struct allocinfo_get_at params = {0};
 	__u64 skip_count;
+	bool sizes_set;
+	struct alloc_tag_counters counters;
+	struct alloc_tag_counters *counters_ptr = NULL;
 
 	if (copy_from_user(&params, arg, sizeof(params)))
 		return -EFAULT;
@@ -244,9 +269,16 @@ static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg)
 	if (params.filter.mask & ~ALLOCINFO_FILTER_MASKS)
 		return -EINVAL;
 
+	if ((params.filter.mask & ALLOCINFO_FILTER_MASK_MIN_SIZE) &&
+	    (params.filter.mask & ALLOCINFO_FILTER_MASK_MAX_SIZE) &&
+	    params.filter.min_size > params.filter.max_size)
+		return -EINVAL;
+
 	priv = (struct allocinfo_private *)m->private;
 
 	skip_count = params.pos;
+	sizes_set = (params.filter.mask &
+		     (ALLOCINFO_FILTER_MASK_MIN_SIZE | ALLOCINFO_FILTER_MASK_MAX_SIZE));
 
 	mutex_lock(&priv->ioctl_lock);
 	codetag_lock_module_list(alloc_tag_cttype, true);
@@ -261,7 +293,11 @@ static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg)
 	ct = codetag_next_ct(&priv->ioctl_iter);
 
 	while (ct) {
-		if (matches_filter(ct, &priv->filter)) {
+		if (sizes_set) {
+			counters = allocinfo_prefetch_counters(ct);
+			counters_ptr = &counters;
+		}
+		if (matches_filter(ct, &priv->filter, counters_ptr)) {
 			if (skip_count == 0)
 				break;
 			skip_count--;
@@ -270,7 +306,7 @@ static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg)
 	}
 
 	if (ct) {
-		allocinfo_to_params(ct, &params.data);
+		allocinfo_to_params(ct, &params.data, counters_ptr);
 		priv->positioned = true;
 	}
 
@@ -292,9 +328,15 @@ static int allocinfo_ioctl_get_next(struct seq_file *m, void __user *arg)
 	struct codetag *ct;
 	struct allocinfo_tag_data params = {0};
 	int ret = 0;
+	bool sizes_set;
+	struct alloc_tag_counters counters;
+	struct alloc_tag_counters *counters_ptr = NULL;
 
 	priv = (struct allocinfo_private *)m->private;
 
+	sizes_set = (priv->filter.mask &
+		     (ALLOCINFO_FILTER_MASK_MIN_SIZE | ALLOCINFO_FILTER_MASK_MAX_SIZE));
+
 	mutex_lock(&priv->ioctl_lock);
 	codetag_lock_module_list(alloc_tag_cttype, true);
 
@@ -304,10 +346,18 @@ static int allocinfo_ioctl_get_next(struct seq_file *m, void __user *arg)
 	}
 
 	ct = codetag_next_ct(&priv->ioctl_iter);
-	while (ct && !matches_filter(ct, &priv->filter))
+	while (ct) {
+		if (sizes_set) {
+			counters = allocinfo_prefetch_counters(ct);
+			counters_ptr = &counters;
+		}
+		if (matches_filter(ct, &priv->filter, counters_ptr))
+			break;
 		ct = codetag_next_ct(&priv->ioctl_iter);
+	}
+
 	if (ct)
-		allocinfo_to_params(ct, &params);
+		allocinfo_to_params(ct, &params, counters_ptr);
 
 	if (!ct) {
 		priv->positioned = false;
-- 
2.54.0.746.g67dd491aae-goog

[PATCH v2 4/6] alloc_tag: add accuracy based filtering to ioctl

[Abhishek Bapat]

Extend the allocinfo filtering mechanism to allow users to filter tags
based on their accuracy.

Signed-off-by: Abhishek Bapat <abhishekbapat@google.com>
---
 include/uapi/linux/alloc_tag.h | 3 +++
 lib/alloc_tag.c                | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h
index 45f158bee0a6..6c4c0e609cd9 100644
--- a/include/uapi/linux/alloc_tag.h
+++ b/include/uapi/linux/alloc_tag.h
@@ -20,6 +20,7 @@ struct allocinfo_tag {
 	char function[ALLOCINFO_STR_SIZE];
 	char filename[ALLOCINFO_STR_SIZE];
 	__u64 lineno;
+	__u64 inaccurate;
 };
 
 struct allocinfo_counter {
@@ -39,6 +40,7 @@ enum {
 	ALLOCINFO_FILTER_FUNCTION,
 	ALLOCINFO_FILTER_FILENAME,
 	ALLOCINFO_FILTER_LINENO,
+	ALLOCINFO_FILTER_INACCURATE,
 	ALLOCINFO_FILTER_MIN_SIZE,
 	ALLOCINFO_FILTER_MAX_SIZE,
 	__ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_MAX_SIZE
@@ -48,6 +50,7 @@ enum {
 #define ALLOCINFO_FILTER_MASK_FUNCTION		(1 << ALLOCINFO_FILTER_FUNCTION)
 #define ALLOCINFO_FILTER_MASK_FILENAME		(1 << ALLOCINFO_FILTER_FILENAME)
 #define ALLOCINFO_FILTER_MASK_LINENO		(1 << ALLOCINFO_FILTER_LINENO)
+#define ALLOCINFO_FILTER_MASK_INACCURATE	(1 << ALLOCINFO_FILTER_INACCURATE)
 #define ALLOCINFO_FILTER_MASK_MIN_SIZE		(1 << ALLOCINFO_FILTER_MIN_SIZE)
 #define ALLOCINFO_FILTER_MASK_MAX_SIZE		(1 << ALLOCINFO_FILTER_MAX_SIZE)
 
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 6c8743eead2d..b1fc14eed7f2 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -217,6 +217,8 @@ static int allocinfo_ioctl_get_content_id(struct seq_file *m, void __user *arg)
 static bool matches_filter(struct codetag *ct, struct allocinfo_filter *filter,
 			   struct alloc_tag_counters *counters)
 {
+	bool inaccurate;
+
 	if (!filter || !filter->mask)
 		return true;
 
@@ -239,6 +241,12 @@ static bool matches_filter(struct codetag *ct, struct allocinfo_filter *filter,
 	    ct->lineno != filter->fields.lineno)
 		return false;
 
+	if (filter->mask & ALLOCINFO_FILTER_MASK_INACCURATE) {
+		inaccurate = !!(ct->flags & CODETAG_FLAG_INACCURATE);
+		if (inaccurate != filter->fields.inaccurate)
+			return false;
+	}
+
 	if ((filter->mask & ALLOCINFO_FILTER_MASK_MIN_SIZE) ||
 	    (filter->mask & ALLOCINFO_FILTER_MASK_MAX_SIZE)) {
 		/* We assume counters is not NULL here as per caller logic */
-- 
2.54.0.746.g67dd491aae-goog

[PATCH v2 5/6] kselftest: alloc_tag: add kselftest for ioctl interface

[Abhishek Bapat]

Introduce a kselftest to verify the new IOCTL-based interface for
/proc/allocinfo. The test covers:

1. Validation of the filename filter.
2. Validation of the function filter.

The first test validates the functionality of the filename filter. Using
"mm/memory.c" as the candidate filename filter, it retrieves filtered
entries from both procfs and ioctl and matches the first VEC_MAX_ENTRIES
entries.

The second test validates the functionality of the function filter.
It uses "dup_mm" as the candidate function as we do not expect this
function name to change frequently and hence won't be needing to modify
this test often.

Note that both the tests match line no, function name and file name
fields. Bytes allocated and calls are not matched as those values may
change in the time when the data is being read from procfs and ioctl and
hence can lead to false negatives.

Signed-off-by: Abhishek Bapat <abhishekbapat@google.com>
---
 MAINTAINERS                                   |   1 +
 tools/testing/selftests/alloc_tag/Makefile    |   9 +
 .../alloc_tag/allocinfo_ioctl_test.c          | 313 ++++++++++++++++++
 3 files changed, 323 insertions(+)
 create mode 100644 tools/testing/selftests/alloc_tag/Makefile
 create mode 100644 tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c

diff --git a/MAINTAINERS b/MAINTAINERS
index d176bde8fbfc..6d57ab4dfb8f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -16711,6 +16711,7 @@ F:	include/linux/alloc_tag.h
 F:	include/linux/pgalloc_tag.h
 F:	include/uapi/linux/alloc_tag.h
 F:	lib/alloc_tag.c
+F:	tools/testing/selftests/alloc_tag/
 
 MEMORY CONTROLLER DRIVERS
 M:	Krzysztof Kozlowski <krzk@kernel.org>
diff --git a/tools/testing/selftests/alloc_tag/Makefile b/tools/testing/selftests/alloc_tag/Makefile
new file mode 100644
index 000000000000..f2b8fc022c3b
--- /dev/null
+++ b/tools/testing/selftests/alloc_tag/Makefile
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+
+TEST_GEN_PROGS := allocinfo_ioctl_test
+
+CFLAGS += -Wall
+CFLAGS += -I../../../../usr/include
+
+include ../lib.mk
+
diff --git a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
new file mode 100644
index 000000000000..5c3c16e86c23
--- /dev/null
+++ b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
@@ -0,0 +1,313 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/* kselftest for allocinfo ioctl
+ * allocinfo ioctl retrives allocinfo data through ioctl
+ * Copyright (C) 2026 Google, Inc.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <linux/types.h>
+#include <linux/alloc_tag.h>
+#include "../kselftest.h"
+
+#define MAX_LINE_LEN		512
+#define ALLOCINFO_PROC		"/proc/allocinfo"
+
+enum ioctl_ret {
+	IOCTL_SUCCESS = 0,
+	IOCTL_FAILURE = 1,
+	IOCTL_INVALID_DATA = 2,
+};
+
+#define VEC_MAX_ENTRIES 32
+
+struct allocinfo_tag_data_vec {
+	struct allocinfo_tag_data tag[VEC_MAX_ENTRIES];
+	__u64 count;
+};
+
+static inline int __allocinfo_get_content_id(int dev_fd, struct allocinfo_content_id *params)
+{
+	return ioctl(dev_fd, ALLOCINFO_IOC_CONTENT_ID, params);
+}
+
+static inline int __allocinfo_get_at(int dev_fd, struct allocinfo_get_at *params)
+{
+	return ioctl(dev_fd, ALLOCINFO_IOC_GET_AT, params);
+}
+
+static inline int __allocinfo_get_next(int dev_fd, struct allocinfo_tag_data *params)
+{
+	return ioctl(dev_fd, ALLOCINFO_IOC_GET_NEXT, params);
+}
+
+static bool match_entry(const struct allocinfo_tag_data *procfs_entry,
+			const struct allocinfo_tag_data *tag_data,
+			bool match_bytes, bool match_calls, bool match_lineno,
+			bool match_function, bool match_filename)
+{
+	if (match_bytes && tag_data->counter.bytes != procfs_entry->counter.bytes) {
+		ksft_print_msg("size retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+
+	if (match_calls && tag_data->counter.calls != procfs_entry->counter.calls) {
+		ksft_print_msg("call count retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+
+	if (match_lineno && tag_data->tag.lineno != procfs_entry->tag.lineno) {
+		ksft_print_msg("lineno retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+
+	if (match_function &&
+	    strncmp(tag_data->tag.function, procfs_entry->tag.function, ALLOCINFO_STR_SIZE)) {
+		ksft_print_msg("function retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+
+	if (match_filename &&
+	    strncmp(tag_data->tag.filename, procfs_entry->tag.filename, ALLOCINFO_STR_SIZE)) {
+		ksft_print_msg("filename retrieved through ioctl does not match procfs\n");
+		return false;
+	}
+	return true;
+}
+
+static bool match_entries(const struct allocinfo_tag_data_vec *procfs_entries,
+			  const struct allocinfo_tag_data_vec *tags,
+			  bool match_bytes, bool match_calls, bool match_lineno,
+			  bool match_function, bool match_filename)
+{
+	__u64 i;
+
+	if (procfs_entries->count != tags->count) {
+		ksft_print_msg("Entry count mismatch. ioctl entries: %llu, proc entries: %llu\n",
+			       tags->count, procfs_entries->count);
+		return false;
+	}
+	for (i = 0; i < procfs_entries->count; i++) {
+		if (!match_entry(&procfs_entries->tag[i], &tags->tag[i],
+				 match_bytes, match_calls, match_lineno,
+				 match_function, match_filename)) {
+			ksft_print_msg("%lluth entry does not match.\n", i);
+			return false;
+		}
+	}
+	return true;
+}
+
+static int get_filtered_procfs_entries(struct allocinfo_tag_data_vec *procfs_entries,
+				       const struct allocinfo_filter *filter, int fd)
+{
+	FILE *fp = fdopen(fd, "r");
+	char line[MAX_LINE_LEN];
+	int matches;
+	struct allocinfo_tag_data procfs_entry;
+
+	if (!fp) {
+		ksft_print_msg("Failed to open " ALLOCINFO_PROC " for reading\n");
+		return 1;
+	}
+	memset(procfs_entries, 0, sizeof(*procfs_entries));
+	while (fgets(line, sizeof(line), fp) && procfs_entries->count < VEC_MAX_ENTRIES) {
+
+		memset(&procfs_entry, 0, sizeof(procfs_entry));
+		matches = sscanf(line, "%llu %llu %[^:]:%llu func:%s",
+				 &procfs_entry.counter.bytes,
+				 &procfs_entry.counter.calls,
+				 procfs_entry.tag.filename,
+				 &procfs_entry.tag.lineno,
+				 procfs_entry.tag.function);
+
+		if (matches != 5)
+			continue;
+
+		if (filter->mask & ALLOCINFO_FILTER_MASK_FILENAME) {
+			if (strncmp(procfs_entry.tag.filename,
+				    filter->fields.filename, ALLOCINFO_STR_SIZE))
+				continue;
+		}
+		if (filter->mask & ALLOCINFO_FILTER_MASK_FUNCTION) {
+			if (strncmp(procfs_entry.tag.function,
+				    filter->fields.function, ALLOCINFO_STR_SIZE))
+				continue;
+		}
+		if (filter->mask & ALLOCINFO_FILTER_MASK_LINENO) {
+			if (procfs_entry.tag.lineno != filter->fields.lineno)
+				continue;
+		}
+		if (filter->mask & ALLOCINFO_FILTER_MASK_MIN_SIZE) {
+			if (procfs_entry.counter.bytes < filter->min_size)
+				continue;
+		}
+		if (filter->mask & ALLOCINFO_FILTER_MASK_MAX_SIZE) {
+			if (procfs_entry.counter.bytes > filter->max_size)
+				continue;
+		}
+
+		memcpy(&procfs_entries->tag[procfs_entries->count++], &procfs_entry,
+		       sizeof(procfs_entry));
+	}
+	return 0;
+}
+
+static enum ioctl_ret get_filtered_ioctl_entries(struct allocinfo_tag_data_vec *tags,
+						 const struct allocinfo_filter *filter, int fd,
+						 __u64 start_pos)
+{
+	struct allocinfo_content_id start_cont_id, end_cont_id;
+	struct allocinfo_get_at get_at_params;
+	const int max_retries = 10;
+	int retry_count = 0;
+	int status;
+
+	/*
+	 * __allocinfo_get_content_id may return different values if a kernel module was loaded
+	 * between the two calls. If that happens, the data gathered cannot be considered consistent
+	 * and hence needs to be fetched again to avoid flakiness.
+	 */
+	do {
+		if (__allocinfo_get_content_id(fd, &start_cont_id)) {
+			ksft_print_msg("allocinfo_get_content_id failed\n");
+			return IOCTL_FAILURE;
+		}
+
+		memset(tags, 0, sizeof(*tags));
+		memset(&get_at_params, 0, sizeof(get_at_params));
+		memcpy(&get_at_params.filter, filter, sizeof(*filter));
+		get_at_params.pos = start_pos;
+		if (__allocinfo_get_at(fd, &get_at_params)) {
+			ksft_print_msg("allocinfo_get_at failed\n");
+			return IOCTL_FAILURE;
+		}
+		memcpy(&tags->tag[tags->count++], &get_at_params.data, sizeof(get_at_params.data));
+
+		while (tags->count < VEC_MAX_ENTRIES &&
+		       __allocinfo_get_next(fd, &tags->tag[tags->count]) == 0)
+			tags->count++;
+
+		if (__allocinfo_get_content_id(fd, &end_cont_id)) {
+			ksft_print_msg("allocinfo_get_content_id failed\n");
+			return IOCTL_FAILURE;
+		}
+
+		if (start_cont_id.id == end_cont_id.id) {
+			status = IOCTL_SUCCESS;
+		} else {
+			ksft_print_msg("allocinfo_get_content_id mismatch, retrying...\n");
+			status = IOCTL_INVALID_DATA;
+		}
+	} while (status == IOCTL_INVALID_DATA && retry_count++ < max_retries);
+
+	return status;
+}
+
+static int run_filter_test(const struct allocinfo_filter *filter)
+{
+	int fd;
+	struct allocinfo_tag_data_vec *tags = malloc(sizeof(*tags));
+	struct allocinfo_tag_data_vec *procfs_entries = malloc(sizeof(*procfs_entries));
+	int ioctl_status;
+	int ret = KSFT_PASS;
+
+	if (!tags || !procfs_entries) {
+		ksft_print_msg("Memory allocation failed.\n");
+		ret = KSFT_FAIL;
+		goto freemem;
+	}
+
+	fd = open(ALLOCINFO_PROC, O_RDONLY);
+	if (fd < 0) {
+		ksft_exit_skip("Failed to open " ALLOCINFO_PROC ": %s\n", strerror(errno));
+		ret = KSFT_FAIL;
+		goto freemem;
+	}
+
+	if (get_filtered_procfs_entries(procfs_entries, filter, fd)) {
+		ksft_print_msg("Error retrieving entries from " ALLOCINFO_PROC "\n");
+		ret = KSFT_FAIL;
+		goto exit;
+	}
+
+	if (procfs_entries->count == 0) {
+		ksft_print_msg("No entries found in " ALLOCINFO_PROC ", skipping test\n");
+		ret = KSFT_SKIP;
+		goto exit;
+	}
+
+	ioctl_status = get_filtered_ioctl_entries(tags, filter, fd, 0);
+	if (ioctl_status == IOCTL_INVALID_DATA) {
+		ksft_print_msg("Trouble retrieving valid IOCTL entries, skipping.\n");
+		ret = KSFT_SKIP;
+		goto exit;
+	}
+	if (ioctl_status == IOCTL_FAILURE) {
+		ksft_print_msg("Error retrieving IOCTL entries.\n");
+		ret = KSFT_FAIL;
+		goto exit;
+	}
+
+	if (!match_entries(procfs_entries, tags, false, false, true, true, true))
+		ret = KSFT_FAIL;
+
+exit:
+	close(fd);
+freemem:
+	free(tags);
+	free(procfs_entries);
+	return ret;
+}
+
+static int test_filename_filter(void)
+{
+	struct allocinfo_filter filter;
+	const char *target_filename = "mm/memory.c";
+
+	memset(&filter, 0, sizeof(filter));
+	filter.mask |= ALLOCINFO_FILTER_MASK_FILENAME;
+	strncpy(filter.fields.filename, target_filename, ALLOCINFO_STR_SIZE);
+
+	return run_filter_test(&filter);
+}
+
+static int test_function_filter(void)
+{
+	struct allocinfo_filter filter;
+	const char *target_function = "dup_mm";
+
+	memset(&filter, 0, sizeof(filter));
+	filter.mask |= ALLOCINFO_FILTER_MASK_FUNCTION;
+	strncpy(filter.fields.function, target_function, ALLOCINFO_STR_SIZE);
+
+	return run_filter_test(&filter);
+}
+
+int main(int argc, char *argv[])
+{
+	int ret;
+
+	ksft_set_plan(2);
+
+	ret = test_filename_filter();
+	if (ret == KSFT_SKIP)
+		ksft_test_result_skip("Skipping test_filename_filter\n");
+	else
+		ksft_test_result(ret == KSFT_PASS, "test_filename_filter\n");
+
+	ret = test_function_filter();
+	if (ret == KSFT_SKIP)
+		ksft_test_result_skip("Skipping test_function_filter\n");
+	else
+		ksft_test_result(ret == KSFT_PASS, "test_function_filter\n");
+
+	ksft_finished();
+}
-- 
2.54.0.746.g67dd491aae-goog

[PATCH v2 6/6] kselftest: alloc_tag: extend the allocinfo ioctl kselftest

[Abhishek Bapat]

Add the following 2 scenarios to the allocinfo ioctl kselftest:
1. Validate size based filtering
2. Validate lineno based filtering

The first test uses "do_init_module" as the candidate function for the
test. This is because the associated site will only allocate memory when
a kernel module is loaded. The return value of get_content_id() changes
every time modules are loaded or unloaded. Hence, as long as
get_content_id() values at the start and the end of the test are the
same, the memory allocated by the do_init_module call site should also
remain the same. Consequently, the test can assume consistency between
the value returned by the ioctl and the procfs resulting in less
flakiness.

Signed-off-by: Abhishek Bapat <abhishekbapat@google.com>
---
 .../alloc_tag/allocinfo_ioctl_test.c          | 194 +++++++++++++++++-
 1 file changed, 193 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
index 5c3c16e86c23..ce3576e3cd9b 100644
--- a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
+++ b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c
@@ -291,11 +291,191 @@ static int test_function_filter(void)
 	return run_filter_test(&filter);
 }
 
+static int test_size_filter(void)
+{
+	int fd;
+	struct allocinfo_tag_data_vec *tags = malloc(sizeof(*tags));
+	struct allocinfo_tag_data_vec *procfs_entries = malloc(sizeof(*procfs_entries));
+	struct allocinfo_filter filter;
+	int ret = KSFT_PASS;
+	__u64 target_size, i;
+	bool found = false;
+	const char *target_function = "do_init_module";
+
+	if (!tags || !procfs_entries) {
+		ksft_print_msg("Memory allocation failed.\n");
+		ret = KSFT_FAIL;
+		goto freemem;
+	}
+
+	fd = open(ALLOCINFO_PROC, O_RDONLY);
+	if (fd < 0) {
+		ksft_exit_skip("Failed to open " ALLOCINFO_PROC ": %s\n", strerror(errno));
+		ret = KSFT_FAIL;
+		goto freemem;
+	}
+
+	memset(&filter, 0, sizeof(filter));
+	filter.mask |= ALLOCINFO_FILTER_MASK_FUNCTION;
+	strncpy(filter.fields.function, target_function, ALLOCINFO_STR_SIZE);
+
+	if (get_filtered_procfs_entries(procfs_entries, &filter, fd)) {
+		ksft_print_msg("Error retrieving entries from " ALLOCINFO_PROC "\n");
+		ret = KSFT_FAIL;
+		goto exit;
+	}
+
+	if (procfs_entries->count == 0) {
+		ksft_print_msg("Function %s not found in procfs\n", target_function);
+		ret = KSFT_SKIP;
+		goto exit;
+	}
+
+	/*
+	 * We depend on the result of procfs entries to create the ioctl_filter. Hence we
+	 * cannot recycle the run_filter_test function here.
+	 */
+	target_size = procfs_entries->tag[0].counter.bytes;
+
+	memset(&filter, 0, sizeof(filter));
+	filter.mask |= ALLOCINFO_FILTER_MASK_MIN_SIZE | ALLOCINFO_FILTER_MASK_MAX_SIZE;
+	filter.min_size = target_size;
+	filter.max_size = target_size;
+
+	__u64 pos = 0;
+	enum ioctl_ret ioctl_status;
+
+	/*
+	 * This loop is required because the first 32 entries fetched by the IOCTL based on
+	 * the size parameter might not contain the exact entry that was used from procfs.
+	 * If that happens, we must update pos and fetch again until we find the exact entry.
+	 */
+	while (1) {
+		ioctl_status = get_filtered_ioctl_entries(tags, &filter, fd, pos);
+		if (ioctl_status == IOCTL_INVALID_DATA) {
+			ksft_print_msg("Trouble retrieving valid IOCTL entries, skipping.\n");
+			ret = KSFT_SKIP;
+			goto exit;
+		}
+		if (ioctl_status == IOCTL_FAILURE) {
+			ksft_print_msg("Error retrieving IOCTL entries.\n");
+			ret = KSFT_FAIL;
+			goto exit;
+		}
+
+		for (i = 0; i < tags->count; i++) {
+			if (strcmp(tags->tag[i].tag.function, target_function) == 0) {
+				found = true;
+				break;
+			}
+		}
+
+		if (found)
+			break;
+
+		if (tags->count < VEC_MAX_ENTRIES)
+			break;
+
+		pos += tags->count;
+	}
+
+	if (!found) {
+		ksft_print_msg("Entry with function %s not found in IOCTL results\n",
+			       target_function);
+		ret = KSFT_FAIL;
+	}
+
+exit:
+	close(fd);
+freemem:
+	free(tags);
+	free(procfs_entries);
+	return ret;
+}
+
+static int test_lineno_filter(void)
+{
+	int fd;
+	struct allocinfo_tag_data_vec *tags = malloc(sizeof(*tags));
+	struct allocinfo_tag_data_vec *procfs_entries = malloc(sizeof(*procfs_entries));
+	struct allocinfo_filter filter;
+	enum ioctl_ret ioctl_status;
+	int ret = KSFT_PASS;
+	__u64 target_lineno, i;
+
+	if (!tags || !procfs_entries) {
+		ksft_print_msg("Memory allocation failed.\n");
+		ret = KSFT_FAIL;
+		goto freemem;
+	}
+
+	fd = open(ALLOCINFO_PROC, O_RDONLY);
+	if (fd < 0) {
+		ksft_exit_skip("Failed to open " ALLOCINFO_PROC ": %s\n", strerror(errno));
+		ret = KSFT_FAIL;
+		goto freemem;
+	}
+
+	memset(&filter, 0, sizeof(filter));
+
+	if (get_filtered_procfs_entries(procfs_entries, &filter, fd)) {
+		ksft_print_msg("Error retrieving entries from " ALLOCINFO_PROC "\n");
+		ret = KSFT_FAIL;
+		goto exit;
+	}
+	if (procfs_entries->count == 0) {
+		ksft_print_msg("Could not retrieve procfs entries\n");
+		ret = KSFT_SKIP;
+		goto exit;
+	}
+	/*
+	 * We depend on the result of procfs entries to create the ioctl_filter. Hence we
+	 * cannot recycle the run_filter_test function here.
+	 */
+	target_lineno = procfs_entries->tag[0].tag.lineno;
+
+	filter.mask |= ALLOCINFO_FILTER_MASK_LINENO;
+	filter.fields.lineno = target_lineno;
+
+	ioctl_status = get_filtered_ioctl_entries(tags, &filter, fd, 0);
+	if (ioctl_status == IOCTL_INVALID_DATA) {
+		ksft_print_msg("Trouble retrieving valid IOCTL entries, skipping.\n");
+		ret = KSFT_SKIP;
+		goto exit;
+	}
+	if (ioctl_status == IOCTL_FAILURE) {
+		ksft_print_msg("Error retrieving IOCTL entries.\n");
+		ret = KSFT_FAIL;
+		goto exit;
+	}
+
+	if (tags->count == 0) {
+		ksft_print_msg("IOCTL returned 0 matches for target lineno %llu.\n", target_lineno);
+		ret = KSFT_FAIL;
+		goto exit;
+	}
+	for (i = 0; i < tags->count; i++) {
+		if (tags->tag[i].tag.lineno != target_lineno) {
+			ksft_print_msg("IOCTL entry %llu has incorrect lineno %llu.\n",
+				       i, tags->tag[i].tag.lineno);
+			ret = KSFT_FAIL;
+			goto exit;
+		}
+	}
+
+exit:
+	close(fd);
+freemem:
+	free(tags);
+	free(procfs_entries);
+	return ret;
+}
+
 int main(int argc, char *argv[])
 {
 	int ret;
 
-	ksft_set_plan(2);
+	ksft_set_plan(4);
 
 	ret = test_filename_filter();
 	if (ret == KSFT_SKIP)
@@ -309,5 +489,17 @@ int main(int argc, char *argv[])
 	else
 		ksft_test_result(ret == KSFT_PASS, "test_function_filter\n");
 
+	ret = test_size_filter();
+	if (ret == KSFT_SKIP)
+		ksft_test_result_skip("Skipping test_size_filter\n");
+	else
+		ksft_test_result(ret == KSFT_PASS, "test_size_filter\n");
+
+	ret = test_lineno_filter();
+	if (ret == KSFT_SKIP)
+		ksft_test_result_skip("Skipping test_lineno_filter\n");
+	else
+		ksft_test_result(ret == KSFT_PASS, "test_lineno_filter\n");
+
 	ksft_finished();
 }
-- 
2.54.0.746.g67dd491aae-goog

Re: [PATCH v2 0/6] alloc_tag: introduce IOCTL-based filtering for MAP

[Andrew Morton]

On Fri, 22 May 2026 17:45:32 +0000 Abhishek Bapat <abhishekbapat@google.com> wrote:

> Currently, memory allocation profiling data is primarily exposed through
> /proc/allocinfo. While useful for manual inspection, this text-based
> interface poses challenges for production monitoring and large-scale
> analysis:
> 
> 1. Userspace must parse large amounts of text to extract specific
> fields.
> 2. To find specific tags, userspace must read the entire dataset,
> requiring many context switches and high data copying.
> 3. The kernel currently aggregates per-CPU counters for every allocation
> size, even those the user intends to filter out immediately.
> 
> This series introduces a new IOCTL-based binary interface for allocinfo
> that supports kernel-side filtering. By allowing the user to specify a
> filter mask, we significantly reduce the work performed in-kernel and
> the amount of data transferred to userspace.
> 
> Performance measurements were conducted on an Intel Xeon Platinum 8481C
> (224 CPUs) with caches dropped before each run.
> 
> The IOCTL mechanism shows a ~20x performance improvement for
> filtered queries. The kernel avoids the expensive per-CPU counter
> aggregation (alloc_tag_read) for any tags that fail the initial string
> or location filters.
> 
> Scenario 1: Specific File Filtering (arch/x86/events/rapl.c)
> 1. Traditional (cat /proc/allocinfo | grep): 22ms (sys)
> 2. IOCTL Interface: 1ms (sys)
> 
> Scenario 2: Compound Filtering (Filename + Size)
> 1. Traditional: (cat ... | grep | awk): 21ms (sys)
> 2. IOCTL Interface: 1ms (sys)
> 
> Scenario 3: Size-Based Filtering (min_size = 1MB)
> 1. Traditional: (cat ... | awk): 21ms (sys)
> 2. IOCTL Interface: 14ms (sys)

Yup, textual interfaces aren't fast.

And ioctl-baed interfaces aren't popular.  One would prefer to see an
interface which uses read()/lseek(), pread(), etc.  It would be
appropriate for this [0/N] to have a discussion of why that approach
was not chosen.

>  .../userspace-api/ioctl/ioctl-number.rst      |   2 +
>  MAINTAINERS                                   |   2 +
>  include/linux/codetag.h                       |   1 +
>  include/uapi/linux/alloc_tag.h                |  87 +++
>  lib/alloc_tag.c                               | 303 ++++++++++-
>  lib/codetag.c                                 |  11 +
>  tools/testing/selftests/alloc_tag/Makefile    |   9 +
>  .../alloc_tag/allocinfo_ioctl_test.c          | 505 ++++++++++++++++++
>  8 files changed, 918 insertions(+), 2 deletions(-)
>  create mode 100644 include/uapi/linux/alloc_tag.h
>  create mode 100644 tools/testing/selftests/alloc_tag/Makefile
>  create mode 100644 tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c

At some point this should grow user-facing documentation, please.

And the right time for that is now, because such documentation is
useful for code review - it makes that review both easier and more
useful.

Sashiko had a few things to say:

	https://sashiko.dev/#/patchset/cover.1779471082.git.abhishekbapat@google.com

Re: [PATCH v2 1/6] alloc_tag: add ioctl to /proc/allocinfo

[Andrew Morton]

On Fri, 22 May 2026 17:45:33 +0000 Abhishek Bapat <abhishekbapat@google.com> wrote:

> From: Suren Baghdasaryan <surenb@google.com>
> 
> Add the following ioctl commands for /proc/allocinfo file:
> 
> ALLOCINFO_IOC_CONTENT_ID - gets content identifier which can be used
> to check whether the file content has changed specifically due to module
> load/unload. Every time a module is loaded / unloaded, the returned
> value will be different. By comparing the identifier value at the
> beginning and at the end of the content retrieval operation, users can
> validate retrieved information for consistency.
> 
> ALLOCINFO_IOC_GET_AT - gets the record at the specified position. This
> is the position of a record in /proc/allocinfo.
> 
> ALLOCINFO_IOC_GET_NEXT - gets the record next to the last retrieved
> one. If no records were previously retrieved, returns the first
> record.
> 
> index 000000000000..e9a5b55fcc7a
> --- /dev/null
> +++ b/include/uapi/linux/alloc_tag.h
> @@ -0,0 +1,54 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +/*
> + *  include/linux/alloc_tag.h
> + */
> +
> +#ifndef _UAPI_ALLOC_TAG_H
> +#define _UAPI_ALLOC_TAG_H
> +
> +#include <linux/types.h>
> +
> +#define ALLOCINFO_STR_SIZE	64
> +
> +struct allocinfo_content_id {
> +	__u64 id;
> +};
> +
> +struct allocinfo_tag {
> +	/* Longer names are trimmed */
> +	char modname[ALLOCINFO_STR_SIZE];
> +	char function[ALLOCINFO_STR_SIZE];
> +	char filename[ALLOCINFO_STR_SIZE];
> +	__u64 lineno;
> +};
> +
> +struct allocinfo_counter {
> +	__u64 bytes;
> +	__u64 calls;
> +	__u8 accurate;
> +	__u8 pad[7]; /* Add alignment to not break the 32-bit compatible interface */

This seems rather fragile, and makes assumptions about compiler layout?

Can't we use __attribute__((aligned)) in some fashion?

> +};
> +
> +struct allocinfo_tag_data {
> +	struct allocinfo_tag tag;
> +	struct allocinfo_counter counter;
> +};
> +
> +struct allocinfo_get_at {
> +	__u64 pos;	/* input */
> +	struct allocinfo_tag_data data;
> +};
> +
> +#define _ALLOCINFO_IOC_CONTENT_ID	0
> +#define _ALLOCINFO_IOC_GET_AT		1
> +#define _ALLOCINFO_IOC_GET_NEXT		2
> +
> +#define ALLOCINFO_IOC_BASE		0xA6
> +#define ALLOCINFO_IOC_CONTENT_ID	_IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_CONTENT_ID,	\
> +					     struct allocinfo_content_id)
> +#define ALLOCINFO_IOC_GET_AT		_IOWR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_AT,	\
> +					      struct allocinfo_get_at)
> +#define ALLOCINFO_IOC_GET_NEXT		_IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_NEXT,	\
> +					     struct allocinfo_tag_data)
> +
> +#endif /* _UAPI_ALLOC_TAG_H */
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index b9ca95d1f506..3598735b6c93 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -5,6 +5,7 @@
>  #include <linux/gfp.h>
>  #include <linux/kallsyms.h>
>  #include <linux/module.h>
> +#include <linux/mutex.h>
>  #include <linux/page_ext.h>
>  #include <linux/pgalloc_tag.h>
>  #include <linux/proc_fs.h>
> @@ -14,6 +15,7 @@
>  #include <linux/string_choices.h>
>  #include <linux/vmalloc.h>
>  #include <linux/kmemleak.h>
> +#include <uapi/linux/alloc_tag.h>
>  
>  #define ALLOCINFO_FILE_NAME		"allocinfo"
>  #define MODULE_ALLOC_TAG_VMAP_SIZE	(100000UL * sizeof(struct alloc_tag))
> @@ -46,6 +48,10 @@ int alloc_tag_ref_offs;
>  struct allocinfo_private {
>  	struct codetag_iterator iter;
>  	bool print_header;
> +	/* ioctl uses a separate iterator not to interfere with reads */
> +	struct codetag_iterator ioctl_iter;
> +	bool positioned; /* seq_open_private() sets to 0 */
> +	struct mutex ioctl_lock;
>  };
>  
>  static void *allocinfo_start(struct seq_file *m, loff_t *pos)
> @@ -125,6 +131,190 @@ static const struct seq_operations allocinfo_seq_op = {
>  	.show	= allocinfo_show,
>  };
> 
> +static int allocinfo_open(struct inode *inode, struct file *file)
> +{
> +	int ret;
> +
> +	ret = seq_open_private(file, &allocinfo_seq_op,
> +			       sizeof(struct allocinfo_private));
> +	if (!ret) {
> +		struct seq_file *m = file->private_data;
> +		struct allocinfo_private *priv = m->private;
> +
> +		mutex_init(&priv->ioctl_lock);
> +	}
> +	return ret;
> +}

Generally, the commenting in here is very thin.  Add some explanations
of what the various functions do and, especially, why they do it?

> +static int allocinfo_release(struct inode *inode, struct file *file)
> +{
> +	return seq_release_private(inode, file);
> +}
> +
> +static const char *allocinfo_str(const char *str)
> +{
> +	size_t len = strlen(str);
> +
> +	/* Keep an extra space for the trailing NULL. */
> +	if (len >= ALLOCINFO_STR_SIZE)
> +		str += (len - ALLOCINFO_STR_SIZE) + 1;
> +	return str;
> +}
> +
> +/* Copy a string and trim from the beginning if it's too long */
> +static void allocinfo_copy_str(char *dest, const char *src)
> +{
> +	strscpy(dest, allocinfo_str(src), ALLOCINFO_STR_SIZE);
> +}

See, even these two little functions are unnecessarily difficult to
review when one doesn"t know what they are setting out to do.  One has
to first reverse engineer their intent from the implementation, then
check that the implementation implements that intent.

> +static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg)
> +{
> +	struct allocinfo_private *priv;
> +	struct codetag *ct;
> +	__u64 pos;
> +	struct allocinfo_get_at params = {0};
> +
> +	if (copy_from_user(&params, arg, sizeof(params)))
> +		return -EFAULT;
> +
> +	priv = (struct allocinfo_private *)m->private;

Unneeded cast.

> +	pos = params.pos;
> +
> +	mutex_lock(&priv->ioctl_lock);
> +	codetag_lock_module_list(alloc_tag_cttype, true);
> +
> +	/* Find the codetag */
> +	priv->ioctl_iter = codetag_get_ct_iter(alloc_tag_cttype);
> +	ct = codetag_next_ct(&priv->ioctl_iter);
> +	while (ct && pos--)
> +		ct = codetag_next_ct(&priv->ioctl_iter);
> +	if (ct) {
> +		allocinfo_to_params(ct, &params.data);
> +		priv->positioned = true;
> +	}
> +
> +	codetag_lock_module_list(alloc_tag_cttype, false);
> +	mutex_unlock(&priv->ioctl_lock);
> +
> +	if (!ct)
> +		return -ENOENT;
> +
> +	if (copy_to_user(arg, &params, sizeof(params)))
> +		return -EFAULT;
> +
> +	return 0;
> +}
> +
> +static int allocinfo_ioctl_get_next(struct seq_file *m, void __user *arg)
> +{
> +	struct allocinfo_private *priv;
> +	struct codetag *ct;
> +	struct allocinfo_tag_data params = {0};
> +	int ret = 0;
> +
> +	priv = (struct allocinfo_private *)m->private;

Ditto.

> +	mutex_lock(&priv->ioctl_lock);
> +	codetag_lock_module_list(alloc_tag_cttype, true);
> +
> +	if (!priv->positioned) {
> +		priv->ioctl_iter = codetag_get_ct_iter(alloc_tag_cttype);
> +		priv->positioned = true;
> +	}
> +
> +	ct = codetag_next_ct(&priv->ioctl_iter);
> +	if (ct)
> +		allocinfo_to_params(ct, &params);
> +
> +	if (!ct) {
> +		priv->positioned = false;
> +		ret = -ENOENT;
> +	}
> +	codetag_lock_module_list(alloc_tag_cttype, false);
> +	mutex_unlock(&priv->ioctl_lock);
> +
> +	if (ret == 0) {
> +		if (copy_to_user(arg, &params, sizeof(params)))
> +			return -EFAULT;
> +	}
> +	return ret;
> +}
>
> ...
>