[PATCH/RFC 10/11] numa - Automatic-migration - per proc automigrate kick control

[Lee Schermerhorn <lee.schermerhorn@hp.com>]

AutoPage Migration - add /proc/<tgid>/migrate

Add a "migrate" control file to per process /proc subdir to allow
external trigger of task auto [==self] migration.  When lazy
auto-migration is enabled, this effectively resets all unmappable
pages so that the next touch will cause a migrate on fault, if
the page is remote from the faulting task.  This allows one to
"poke" a task externally to force "re-affinitization on next
touch" independent of inter-node migration.

On read, show current value of task's "migrate_pending".  Nearly
useless, but I wanted to avoid a "write-only" file.

On write, if value is non-zero, set migrate_pending to 1 and set
'NOTIFY_RESUME thread info flag to cause task to handle the pending
migration.  If value is zero, clear the migrate_pending--also not very
useful, but falls out of the code.  Don't bother to reset the thread
info flag when clearing migrate_pending -- just being lazy.  It's a
no-op in this case as far as auto-migration, but might have been set
by something else.

Signed-off-by:  Lee Schermerhorn <lee.schermerhorn@hp.com>

 fs/proc/base.c     |    6 ++++
 fs/proc/internal.h |    2 +
 fs/proc/task_mmu.c |   70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+)

Index: linux-2.6.36-mmotm-101103-1217/fs/proc/base.c
===================================================================
--- linux-2.6.36-mmotm-101103-1217.orig/fs/proc/base.c
+++ linux-2.6.36-mmotm-101103-1217/fs/proc/base.c
@@ -2743,6 +2743,9 @@ static const struct pid_entry tgid_base_
 	REG("maps",       S_IRUGO, proc_maps_operations),
 #ifdef CONFIG_NUMA
 	REG("numa_maps",  S_IRUGO, proc_numa_maps_operations),
+#ifdef CONFIG_AUTO_MIGRATION
+	REG("migrate",    S_IRUGO|S_IWUSR, proc_migrate_operations),
+#endif
 #endif
 	REG("mem",        S_IRUSR|S_IWUSR, proc_mem_operations),
 	LNK("cwd",        proc_cwd_link),
@@ -3080,6 +3083,9 @@ static const struct pid_entry tid_base_s
 	REG("maps",      S_IRUGO, proc_maps_operations),
 #ifdef CONFIG_NUMA
 	REG("numa_maps", S_IRUGO, proc_numa_maps_operations),
+#ifdef CONFIG_AUTO_MIGRATION
+	REG("migrate",   S_IRUGO|S_IWUSR, proc_migrate_operations),
+#endif
 #endif
 	REG("mem",       S_IRUSR|S_IWUSR, proc_mem_operations),
 	LNK("cwd",       proc_cwd_link),
Index: linux-2.6.36-mmotm-101103-1217/fs/proc/internal.h
===================================================================
--- linux-2.6.36-mmotm-101103-1217.orig/fs/proc/internal.h
+++ linux-2.6.36-mmotm-101103-1217/fs/proc/internal.h
@@ -59,6 +59,8 @@ extern const struct file_operations proc
 extern const struct file_operations proc_clear_refs_operations;
 extern const struct file_operations proc_pagemap_operations;
 extern const struct file_operations proc_net_operations;
+extern const struct file_operations proc_migrate_operations;
+
 extern const struct inode_operations proc_net_inode_operations;
 
 void proc_init_inodecache(void);
Index: linux-2.6.36-mmotm-101103-1217/fs/proc/task_mmu.c
===================================================================
--- linux-2.6.36-mmotm-101103-1217.orig/fs/proc/task_mmu.c
+++ linux-2.6.36-mmotm-101103-1217/fs/proc/task_mmu.c
@@ -1016,4 +1016,74 @@ const struct file_operations proc_numa_m
 	.llseek		= seq_lseek,
 	.release	= seq_release_private,
 };
+
+#ifdef CONFIG_AUTO_MIGRATION
+/*
+ * read/write task's "migrate_pending" flag.
+ * on write, set TIF_NOTIFY_RESUME thread info flag so that task
+ * will handle "migrate_pending" on next return to user space --
+ * no later than next clock tick.
+ */
+static ssize_t proc_migrate_read(struct file *file, char __user *buf,
+				  size_t count, loff_t *ppos)
+{
+	struct task_struct *task;
+	char buffer[PROC_NUMBUF];
+	size_t len;
+	int migpend;
+	loff_t __ppos = *ppos;
+
+	task = get_proc_task(file->f_dentry->d_inode);
+	if (!task)
+		return -ESRCH;
+	migpend = task->migrate_pending;
+	put_task_struct(task);
+
+	len = snprintf(buffer, sizeof(buffer), "%i\n", migpend);
+	if (__ppos >= len)
+		return 0;
+	if (count > len-__ppos)
+		count = len-__ppos;
+	if (copy_to_user(buf, buffer + __ppos, count))
+		return -EFAULT;
+	*ppos = __ppos + count;
+	return count;
+}
+
+static ssize_t proc_migrate_write(struct file *file, const char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	struct task_struct *task;
+	char buffer[PROC_NUMBUF], *end;
+	int migpend;
+
+	if (!capable(CAP_SYS_RESOURCE))
+		return -EPERM;
+	memset(buffer, 0, sizeof(buffer));
+	if (count > sizeof(buffer) - 1)
+		count = sizeof(buffer) - 1;
+	if (copy_from_user(buffer, buf, count))
+		return -EFAULT;
+	migpend = simple_strtol(buffer, &end, 0);
+	if (*end == '\n')
+		end++;
+	if (end - buffer == 0)
+		return -EIO;
+
+	task = get_proc_task(file->f_dentry->d_inode);
+	if (!task)
+		return -ESRCH;
+	task->migrate_pending = !!migpend;
+	if (migpend)
+		set_tsk_thread_flag(task, TIF_NOTIFY_RESUME);
+	put_task_struct(task);
+
+	return end - buffer;
+}
+
+const struct file_operations proc_migrate_operations = {
+	.read 		= proc_migrate_read,
+	.write		= proc_migrate_write,
+};
+#endif
 #endif