From 695f055936938c674473ea071ca7359a863551e7 Mon Sep 17 00:00:00 2001
From: Petr Cermak <petrcermak@chromium.org>
Date: Thu, 12 Feb 2015 15:01:00 -0800
Subject: [PATCH] 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.
[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>
---
Documentation/filesystems/proc.txt | 4 ++++
fs/proc/task_mmu.c | 14 ++++++++++++++
include/linux/mm.h | 5 +++++
3 files changed, 23 insertions(+)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index cf8fc2f0b34b..0b3448dba9ec 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -489,6 +489,10 @@ To clear the bits for the file mapped pages associated with the process
To clear the soft-dirty bit
> echo 4 > /proc/PID/clear_refs
+To reset the peak resident set size ("high water mark") to the process's
+current value:
+ > echo 5 > /proc/PID/clear_refs
+
Any other value written to /proc/PID/clear_refs will have no effect.
The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 0e36c1e49fe3..1359a911d194 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -732,6 +732,7 @@ enum clear_refs_types {
CLEAR_REFS_ANON,
CLEAR_REFS_MAPPED,
CLEAR_REFS_SOFT_DIRTY,
+ CLEAR_REFS_MM_HIWATER_RSS,
CLEAR_REFS_LAST,
};
@@ -907,6 +908,18 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
.mm = mm,
.private = &cp,
};
+
+ 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);
if (type == CLEAR_REFS_SOFT_DIRTY) {
for (vma = mm->mmap; vma; vma = vma->vm_next) {
@@ -928,6 +941,7 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
mmu_notifier_invalidate_range_end(mm, 0, -1);
flush_tlb_mm(mm);
up_read(&mm->mmap_sem);
+out_mm:
mmput(mm);
}
put_task_struct(task);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index bd52e2f14027..9bee7ec0c31f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1408,6 +1408,11 @@ static inline void update_hiwater_vm(struct mm_struct *mm)
mm->hiwater_vm = mm->total_vm;
}
+static inline void reset_mm_hiwater_rss(struct mm_struct *mm)
+{
+ mm->hiwater_rss = get_mm_rss(mm);
+}
+
static inline void setmax_mm_hiwater_rss(unsigned long *maxrss,
struct mm_struct *mm)
{
--
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