Re: [PATCH] mm: consider all swapped back pages in used-once logic
From: Michal Hocko
Date: Thu May 17 2012 - 08:11:08 EST
On Thu 17-05-12 02:24:12, Andrew Morton wrote:
> On Thu, 17 May 2012 11:13:53 +0200 Michal Hocko <mhocko@xxxxxxx> wrote:
>
> > [64574746 vmscan: detect mapped file pages used only once] made mapped pages
> > have another round in inactive list because they might be just short
> > lived and so we could consider them again next time. This heuristic
> > helps to reduce pressure on the active list with a streaming IO
> > worklods.
> > 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%
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/