Being able to reset mm->hiwater_rss (resident set size high water mark) from
user space would enable fine grained iterative memory profiling. I propose a
very short patch for doing so below. I would like to get some feedback on the
user-space interface to do this. Would it be best to:
1. Add an extra value to /proc/PID/clear_refs to reset VmHWM? (The proposed
patch uses this approach.)
2. Add a new write-only pseudo-file for this purpose (e.g.,
/proc/pid/reset_hwm)?
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.
Signed-off-by: Petr Cermak <petrcer...@chromium.org>
---
Documentation/filesystems/proc.txt | 3 ++
fs/proc/task_mmu.c | 106 +++++++++++++++++++++----------------
include/linux/mm.h | 5 ++
3 files changed, 68 insertions(+), 46 deletions(-)
diff --git a/Documentation/filesystems/proc.txt
b/Documentation/filesystems/proc.txt
index eb8a10e..2c277e9 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -488,6 +488,9 @@ 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")
+ > 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 4e0388c..86b23b2 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -712,6 +712,7 @@ enum clear_refs_types {
CLEAR_REFS_ANON,
CLEAR_REFS_MAPPED,
CLEAR_REFS_SOFT_DIRTY,
+ CLEAR_REFS_MM_HIWATER_RSS,
CLEAR_REFS_LAST,
};
@@ -818,56 +819,69 @@ static ssize_t clear_refs_write(struct file *file, const
char __user *buf,
return -ESRCH;
mm = get_task_mm(task);
if (mm) {
- struct clear_refs_private cp = {
- .type = type,
- };
- struct mm_walk clear_refs_walk = {
- .pmd_entry = clear_refs_pte_range,
- .mm = mm,
- .private = &cp,
- };
- down_read(&mm->mmap_sem);
- if (type == CLEAR_REFS_SOFT_DIRTY) {
- for (vma = mm->mmap; vma; vma = vma->vm_next) {
- if (!(vma->vm_flags & VM_SOFTDIRTY))
- continue;
- up_read(&mm->mmap_sem);
- down_write(&mm->mmap_sem);
+ if (type == CLEAR_REFS_MM_HIWATER_RSS) {
+ /*
+ * Writing 5 to /proc/pid/clear_refs resets the peak
+ * resident set size.
+ */
+ down_write(&mm->mmap_sem);
+ reset_mm_hiwater_rss(mm);
+ up_write(&mm->mmap_sem);
+ } else {
+ struct clear_refs_private cp = {
+ .type = type,
+ };
+ struct mm_walk clear_refs_walk = {
+ .pmd_entry = clear_refs_pte_range,
+ .mm = mm,
+ .private = &cp,
+ };
+ down_read(&mm->mmap_sem);
+ if (type == CLEAR_REFS_SOFT_DIRTY) {
for (vma = mm->mmap; vma; vma = vma->vm_next) {
- vma->vm_flags &= ~VM_SOFTDIRTY;
- vma_set_page_prot(vma);
+ if (!(vma->vm_flags & VM_SOFTDIRTY))
+ continue;
+ up_read(&mm->mmap_sem);
+ down_write(&mm->mmap_sem);
+ for (vma = mm->mmap; vma;
+ vma = vma->vm_next) {
+ vma->vm_flags &= ~VM_SOFTDIRTY;
+ vma_set_page_prot(vma);
+ }
+ downgrade_write(&mm->mmap_sem);
+ break;
}
- downgrade_write(&mm->mmap_sem);
- break;
+ mmu_notifier_invalidate_range_start(mm, 0, -1);
}
- mmu_notifier_invalidate_range_start(mm, 0, -1);
- }
- for (vma = mm->mmap; vma; vma = vma->vm_next) {
- cp.vma = vma;
- if (is_vm_hugetlb_page(vma))
- continue;
- /*
- * Writing 1 to /proc/pid/clear_refs affects all pages.
- *
- * Writing 2 to /proc/pid/clear_refs only affects
- * Anonymous pages.
- *
- * Writing 3 to /proc/pid/clear_refs only affects file
- * mapped pages.
- *
- * Writing 4 to /proc/pid/clear_refs affects all pages.
- */
- if (type == CLEAR_REFS_ANON && vma->vm_file)
- continue;
- if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
- continue;
- walk_page_range(vma->vm_start, vma->vm_end,
- &clear_refs_walk);
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ cp.vma = vma;
+ if (is_vm_hugetlb_page(vma))
+ continue;
+ /*
+ * Writing 1 to /proc/pid/clear_refs affects all
+ * pages.
+ *
+ * Writing 2 to /proc/pid/clear_refs only
+ * affects Anonymous pages.
+ *
+ * Writing 3 to /proc/pid/clear_refs only
+ * affects file mapped pages.
+ *
+ * Writing 4 to /proc/pid/clear_refs affects all
+ * pages.
+ */
+ if (type == CLEAR_REFS_ANON && vma->vm_file)
+ continue;
+ if (type == CLEAR_REFS_MAPPED && !vma->vm_file)
+ continue;
+ walk_page_range(vma->vm_start, vma->vm_end,
+ &clear_refs_walk);
+ }
+ if (type == CLEAR_REFS_SOFT_DIRTY)
+ mmu_notifier_invalidate_range_end(mm, 0, -1);
+ flush_tlb_mm(mm);
+ up_read(&mm->mmap_sem);
}
- if (type == CLEAR_REFS_SOFT_DIRTY)
- mmu_notifier_invalidate_range_end(mm, 0, -1);
- flush_tlb_mm(mm);
- up_read(&mm->mmap_sem);
mmput(mm);
}
put_task_struct(task);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index b464611..8a51ef4 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1350,6 +1350,11 @@ 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)
{
--
2.2.0.rc0.207.ga3a616c
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