| Message ID | 20220620081251.2928103-1-vincent.whitchurch@axis.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] mm/smaps: add Pss_Dirty | expand |
On Mon, Jun 20, 2022 at 10:12:50AM +0200, Vincent Whitchurch wrote: > Pss is the sum of the sizes of clean and dirty private pages, and the > proportional sizes of clean and dirty shared pages: > > Private = Private_Dirty + Private_Clean > Shared_Proportional = Shared_Dirty_Proportional + Shared_Clean_Proportional > Pss = Private + Shared_Proportional > > The Shared*Proportional fields are not present in smaps, so it is not > always possible to determine how much of the Pss is from dirty pages and > how much is from clean pages. This information can be useful for > measuring memory usage for the purpose of optimisation, since clean > pages can usually be discarded by the kernel immediately while dirty > pages cannot. > > The smaps routines in the kernel already have access to this data, so > add a Pss_Dirty to show it to userspace. Pss_Clean is not added since > it can be calculated from Pss and Pss_Dirty. > > Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> > --- I forgot to include the changelog: v2: - Update Documentation/ABI/testing/procfs-smaps_rollup and Documentation/filesystems/proc.rst. - Move Pss_Dirty next to Pss so that the location is consistent between non-rollup and rollup (since the later has some extra Pss* fields).
diff --git a/Documentation/ABI/testing/procfs-smaps_rollup b/Documentation/ABI/testing/procfs-smaps_rollup index a4e31c465194..b446a7154a1b 100644 --- a/Documentation/ABI/testing/procfs-smaps_rollup +++ b/Documentation/ABI/testing/procfs-smaps_rollup @@ -22,6 +22,7 @@ Description: MMUPageSize: 4 kB Rss: 884 kB Pss: 385 kB + Pss_Dirty: 68 kB Pss_Anon: 301 kB Pss_File: 80 kB Pss_Shmem: 4 kB diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 1bc91fb8c321..f7dce062548f 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -448,6 +448,7 @@ Memory Area, or VMA) there is a series of lines such as the following:: MMUPageSize: 4 kB Rss: 892 kB Pss: 374 kB + Pss_Dirty: 0 kB Shared_Clean: 892 kB Shared_Dirty: 0 kB Private_Clean: 0 kB @@ -479,7 +480,9 @@ dirty shared and private pages in the mapping. The "proportional set size" (PSS) of a process is the count of pages it has in memory, where each page is divided by the number of processes sharing it. So if a process has 1000 pages all to itself, and 1000 shared with one other -process, its PSS will be 1500. +process, its PSS will be 1500. "Pss_Dirty" is the portion of PSS which +consists of dirty pages. ("Pss_Clean" is not included, but it can be +calculated by subtracting "Pss_Dirty" from "Pss".) Note that even a page which is part of a MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used by only one process, is accounted diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 2d04e3470d4c..751c19d5bfdd 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -406,6 +406,7 @@ struct mem_size_stats { u64 pss_anon; u64 pss_file; u64 pss_shmem; + u64 pss_dirty; u64 pss_locked; u64 swap_pss; }; @@ -427,6 +428,7 @@ static void smaps_page_accumulate(struct mem_size_stats *mss, mss->pss_locked += pss; if (dirty || PageDirty(page)) { + mss->pss_dirty += pss; if (private) mss->private_dirty += size; else @@ -808,6 +810,7 @@ static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss, { SEQ_PUT_DEC("Rss: ", mss->resident); SEQ_PUT_DEC(" kB\nPss: ", mss->pss >> PSS_SHIFT); + SEQ_PUT_DEC(" kB\nPss_Dirty: ", mss->pss_dirty >> PSS_SHIFT); if (rollup_mode) { /* * These are meaningful only for smaps_rollup, otherwise two of
Pss is the sum of the sizes of clean and dirty private pages, and the proportional sizes of clean and dirty shared pages: Private = Private_Dirty + Private_Clean Shared_Proportional = Shared_Dirty_Proportional + Shared_Clean_Proportional Pss = Private + Shared_Proportional The Shared*Proportional fields are not present in smaps, so it is not always possible to determine how much of the Pss is from dirty pages and how much is from clean pages. This information can be useful for measuring memory usage for the purpose of optimisation, since clean pages can usually be discarded by the kernel immediately while dirty pages cannot. The smaps routines in the kernel already have access to this data, so add a Pss_Dirty to show it to userspace. Pss_Clean is not added since it can be calculated from Pss and Pss_Dirty. Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> --- Documentation/ABI/testing/procfs-smaps_rollup | 1 + Documentation/filesystems/proc.rst | 5 ++++- fs/proc/task_mmu.c | 3 +++ 3 files changed, 8 insertions(+), 1 deletion(-)