[patch 235/262] mm/damon/dbgfs: support physical memory monitoring

Andrew Morton
2021-11-05T20:47:03Z

From: SeongJae Park <sj@kernel.org>
Subject: mm/damon/dbgfs: support physical memory monitoring

This commit makes the 'damon-dbgfs' to support the physical memory
monitoring, in addition to the virtual memory monitoring.

Users can do the physical memory monitoring by writing a special keyword,
'paddr' to the 'target_ids' debugfs file. Then, DAMON will check the
special keyword and configure the monitoring context to run with the
primitives for the physical address space.

Unlike the virtual memory monitoring, the monitoring target region will
not be automatically set. Therefore, users should also set the monitoring
target address region using the 'init_regions' debugfs file.

Also, note that the physical memory monitoring will not automatically
terminated. The user should explicitly turn off the monitoring by writing
'off' to the 'monitor_on' debugfs file.

Link: https://lkml.kernel.org/r/20211012205711.29216-7-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Amit Shah <amit@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rienjes <rientjes@google.com>
Cc: David Woodhouse <dwmw@amazon.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Leonard Foerster <foersleo@amazon.de>
Cc: Marco Elver <elver@google.com>
Cc: Markus Boehme <markubo@amazon.de>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/damon/Kconfig | 2 +-
mm/damon/dbgfs.c | 21 ++++++++++++++++++---
2 files changed, 19 insertions(+), 4 deletions(-)

--- a/mm/damon/dbgfs.c~mm-damon-dbgfs-support-physical-memory-monitoring
+++ a/mm/damon/dbgfs.c
@@ -339,6 +339,7 @@ static ssize_t dbgfs_target_ids_write(st
const char __user *buf, size_t count, loff_t *ppos)
{
struct damon_ctx *ctx = file->private_data;
+ bool id_is_pid = true;
char *kbuf, *nrs;
unsigned long *targets;
ssize_t nr_targets;
@@ -351,6 +352,11 @@ static ssize_t dbgfs_target_ids_write(st
return PTR_ERR(kbuf);

nrs = kbuf;
+ if (!strncmp(kbuf, "paddr\n", count)) {
+ id_is_pid = false;
+ /* target id is meaningless here, but we set it just for fun */
+ scnprintf(kbuf, count, "42 ");
+ }

targets = str_to_target_ids(nrs, ret, &nr_targets);
if (!targets) {
@@ -358,7 +364,7 @@ static ssize_t dbgfs_target_ids_write(st
goto out;
}

- if (targetid_is_pid(ctx)) {
+ if (id_is_pid) {
for (i = 0; i < nr_targets; i++) {
targets[i] = (unsigned long)find_get_pid(
(int)targets[i]);
@@ -372,15 +378,24 @@ static ssize_t dbgfs_target_ids_write(st

mutex_lock(&ctx->kdamond_lock);
if (ctx->kdamond) {
- if (targetid_is_pid(ctx))
+ if (id_is_pid)
dbgfs_put_pids(targets, nr_targets);
ret = -EBUSY;
goto unlock_out;
}

+ /* remove targets with previously-set primitive */
+ damon_set_targets(ctx, NULL, 0);
+
+ /* Configure the context for the address space type */
+ if (id_is_pid)
+ damon_va_set_primitives(ctx);
+ else
+ damon_pa_set_primitives(ctx);
+
err = damon_set_targets(ctx, targets, nr_targets);
if (err) {
- if (targetid_is_pid(ctx))
+ if (id_is_pid)
dbgfs_put_pids(targets, nr_targets);
ret = err;
}
--- a/mm/damon/Kconfig~mm-damon-dbgfs-support-physical-memory-monitoring
+++ a/mm/damon/Kconfig
@@ -54,7 +54,7 @@ config DAMON_VADDR_KUNIT_TEST

config DAMON_DBGFS
bool "DAMON debugfs interface"
- depends on DAMON_VADDR && DEBUG_FS
+ depends on DAMON_VADDR && DAMON_PADDR && DEBUG_FS
help
This builds the debugfs interface for DAMON. The user space admins
can use the interface for arbitrary data access monitoring.
_