fs/proc/task_mmu.c: add user-space support for resetting mm->hiwater_rss (peak RSS)
Peak resident size of a process can be reset back to the process's
current rss value by writing "5" to /proc/pid/clear_refs. The driving
use-case for this would be getting the peak RSS value, which can be
retrieved from the VmHWM field in /proc/pid/status, per benchmark
iteration or test scenario.
Origin:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=695f055936938c674473ea071ca7359a863551e7
[akpm@linux-foundation.org: clarify behaviour in documentation]
Signed-off-by: Petr Cermak <petrcermak@chromium.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Primiano Tucci <primiano@chromium.org>
Cc: Petr Cermak <petrcermak@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: I543a7640639d9916e813af875003fe3ee3a6bfe0
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e2c925f..e5bc1c7 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -784,6 +784,7 @@
#define CLEAR_REFS_ALL 1
#define CLEAR_REFS_ANON 2
#define CLEAR_REFS_MAPPED 3
+#define CLEAR_REFS_MM_HIWATER_RSS 5
static ssize_t clear_refs_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
@@ -803,7 +804,8 @@
rv = kstrtoint(strstrip(buffer), 10, &type);
if (rv < 0)
return rv;
- if (type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED)
+ if ((type < CLEAR_REFS_ALL || type > CLEAR_REFS_MAPPED) &&
+ type != CLEAR_REFS_MM_HIWATER_RSS)
return -EINVAL;
task = get_proc_task(file_inode(file));
if (!task)
@@ -814,6 +816,18 @@
.pmd_entry = clear_refs_pte_range,
.mm = mm,
};
+
+ if (type == CLEAR_REFS_MM_HIWATER_RSS) {
+ /*
+ * Writing 5 to /proc/pid/clear_refs resets the peak
+ * resident set size to this mm's current rss value.
+ */
+ down_write(&mm->mmap_sem);
+ reset_mm_hiwater_rss(mm);
+ up_write(&mm->mmap_sem);
+ goto out_mm;
+ }
+
down_read(&mm->mmap_sem);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
clear_refs_walk.private = vma;
@@ -837,6 +851,7 @@
}
flush_tlb_mm(mm);
up_read(&mm->mmap_sem);
+out_mm:
mmput(mm);
}
put_task_struct(task);