On Tue, 29 Apr 2008, Ross Biro wrote:
quoted text
> I don't know if this has been noticed before.  I was benchmarking my
> page table relocation code and I noticed that on 2.6.25-rc9 page
> faults take 10% more time than on 2.6.22.  This is using lmbench
> running on an intel x86_64 system.  The good news is that the page
> table relocation code now only adds a 1.6% slow down to page faults.

Do you have CONFIG_CGROUP_MEM_RES_CTLR=y in 2.6.25?
That added about 20% to my lmbench "Page Fault" tests (with
adverse effect on several others e.g. the fork, exec, sh group).

Try the same kernel with boot option "cgroup_disable=memory",
that should recoup most (but not quite all) of the slowdown;
or rebuild with n to CGROUP_MEM_RES_CTLR.

But your "Mmap Latency" went up 425% ??

Hugh

quoted text
> 
>     Ross
> 
> 2.6.25-rc9:
> 
> File & VM system latencies in microseconds - smaller is better
> -------------------------------------------------------------------------------
> Host                 OS   0K File      10K File     Mmap    Prot   Page   100fd
>                         Create Delete Create Delete Latency Fault  Fault  selct
> --------- ------------- ------ ------ ------ ------ ------- ----- ------- -----
> ipnn2     Linux 2.6.25-   13.9 7.6111  103.4 9.7453   926.0 0.711 2.14250 2.552
> ipnn2     Linux 2.6.25-   13.7 7.6243  310.7 9.6574   932.0 0.750 2.15970 2.555
> ipnn2     Linux 2.6.25-   13.9 7.6831  192.5   10.0   927.0 0.760 2.21310 2.553
> ipnn2     Linux 2.6.25-   13.9 7.5739   98.4 9.5330   927.0 0.703 2.17610 2.554
> ipnn2     Linux 2.6.25-   14.6 7.6429   39.1   10.8   935.0 0.763 2.17250 2.552
> ipnn2     Linux 2.6.25-   14.1 7.8777  129.8 9.9375   930.0 0.782 2.26460 2.559
> ipnn2     Linux 2.6.25-   14.8 7.9639  623.8 8.2042   927.0 0.773 2.21510 2.557
> ipnn2     Linux 2.6.25-   14.4 7.5842  622.3 8.3272   920.0 0.745 2.22210 2.558
> ipnn2     Linux 2.6.25-   14.2 7.6339   45.7   10.2   935.0 0.675 2.23860 2.554
> ipnn2     Linux 2.6.25-   14.1 7.7175  263.7   10.1   929.0 0.762 2.22350 2.556
> ipnn2     Linux 2.6.25-   13.9 8.1230  378.2 9.4343   975.0 0.752 2.25920 2.554
> 
> 
> 2.6.23:
> File & VM system latencies in microseconds - smaller is better
> -------------------------------------------------------------------------------
> Host                 OS   0K File      10K File     Mmap    Prot   Page   100fd
>                         Create Delete Create Delete Latency Fault  Fault  selct
> --------- ------------- ------ ------ ------ ------ ------- ----- ------- -----
> ipnn2     Linux 2.6.23-                               218.0 0.912 1.94010 2.626
> ipnn2     Linux 2.6.23-                               219.0 1.095 1.96400 2.597
> ipnn2     Linux 2.6.23-                               219.0 0.774 1.96640 2.603
> ipnn2     Linux 2.6.23-                               221.0 0.946 1.99950 2.601
> ipnn2     Linux 2.6.23-                               219.0 0.902 1.99160 2.733
> ipnn2     Linux 2.6.23-                               217.0 0.904 2.04790 2.601
> ipnn2     Linux 2.6.23-                               225.0 0.893 1.99620 2.600
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