Re: [PATCH 1/1] mm: smaps: split PSS into components

[Luigi Semenzato <semenzato@chromium.org>]

On Wed, Jun 26, 2019 at 3:19 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Wed, 26 Jun 2019 11:04:29 -0700 semenzato@chromium.org wrote:
>
> > From: Luigi Semenzato <semenzato@chromium.org>
> >
> > Report separate components (anon, file, and shmem)
> > for PSS in smaps_rollup.
> >
> > This helps understand and tune the memory manager behavior
> > in consumer devices, particularly mobile devices.  Many of
> > them (e.g. chromebooks and Android-based devices) use zram
> > for anon memory, and perform disk reads for discarded file
> > pages.  The difference in latency is large (e.g. reading
> > a single page from SSD is 30 times slower than decompressing
> > a zram page on one popular device), thus it is useful to know
> > how much of the PSS is anon vs. file.
> >
> > This patch also removes a small code duplication in smaps_account,
> > which would have gotten worse otherwise.
> >
> > Also added missing entry for smaps_rollup in
> > Documentation/filesystems/proc.txt.
> >
> > ...
> >
> > -static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss)
> > +static void __show_smap(struct seq_file *m, const struct mem_size_stats *mss,
> > +     bool rollup_mode)
> >  {
> >       SEQ_PUT_DEC("Rss:            ", mss->resident);
> >       SEQ_PUT_DEC(" kB\nPss:            ", mss->pss >> PSS_SHIFT);
> > +     if (rollup_mode) {
> > +             /*
> > +              * These are meaningful only for smaps_rollup, otherwise two of
> > +              * them are zero, and the other one is the same as Pss.
> > +              */
> > +             SEQ_PUT_DEC(" kB\nPss_Anon:       ",
> > +                     mss->pss_anon >> PSS_SHIFT);
> > +             SEQ_PUT_DEC(" kB\nPss_File:       ",
> > +                     mss->pss_file >> PSS_SHIFT);
> > +             SEQ_PUT_DEC(" kB\nPss_Shmem:      ",
> > +                     mss->pss_shmem >> PSS_SHIFT);
> > +     }
>
> Documentation/filesystems/proc.txt is rather incomplete.  It documents
> /proc/PID/smaps (seems to be out of date) but doesn't describe the
> fields in smaps_rollup.
>
> Please update Documentation/ABI/testing/procfs-smaps_rollup and please
> check that it's up-to-date while you're in there.
>

Thank you for noticing the stale/missing docs and sorry that I did not.
Will email the updated patch shortly.