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SubjectRe: [PATCH] mm: consider all swapped back pages in used-once logic
On Thu 17-05-12 13:23:24, Andrew Morton wrote:
> On Thu, 17 May 2012 14:10:49 +0200
> Michal Hocko <mhocko@suse.cz> wrote:
>
> > > > This patch fixes a regression introduced by this commit for heavy shmem
> > >
> > > A performance regression, specifically.
> > >
> > > Are you able to quantify it?
> >
> > The customer's workload is shmem backed database (80% of RAM) and
> > they are measuring transactions/s with an IO in the background (20%).
> > Transactions touch more or less random rows in the table.
> > The rate goes down drastically when we start swapping out memory.
> >
> > Numbers are more descriptive (without the patch is 100%, with 5
> > representative runs)
> > Average rate 315.83%
> > Best rate 131.76%
> > Worst rate 641.25%
> >
> > Standard deviation (calibrated to average) is ~4% while without the
> > patch we are at 62.82%.
> > The big variance without the patch is caused by the excessive swapping
> > which doesn't occur with the patch applied.
> >
> > * Worst run (100%) compared to a random run with the patch
> > pgpgin pswpin pswpout pgmajfault
> > 1.58% 0.00% 0.01% 0.22%
> >
> > Average size of the LRU lists:
> > nr_inactive_anon nr_active_anon nr_inactive_file nr_active_file
> > 52.91% 7234.72% 249.39% 126.64%
> >
> > * Best run
> > pgpgin pswpin pswpout pgmajfault
> > 3.37% 0.00% 0.11% 0.39%
> >
> > nr_inactive_anon nr_active_anon nr_inactive_file nr_active_file
> > 49.85% 3868.74% 175.03% 121.27%
>
> I turned the above into this soundbite:
>
> : The customer's workload is shmem backed database (80% of RAM) and they are
> : measuring transactions/s with an IO in the background (20%). Transactions
> : touch more or less random rows in the table. Total runtime was
> : approximately tripled by commit 64574746 and this patch restores the
> : previous throughput levels.
>
> Was that truthful?

Total runtime was same for all the runs. It is the number of executed
transactions that was measured. I guess that what you wrote should be
more or less equivalent but it's is not what I have numbers for.
How about:
"
Total number of transactions went down 3 times (in the worst case)
because of commit 64574746. This patch restores the previous numbers.
"

Thanks
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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