linux-kernel - Page Faults slower in 2.6.25-rc9 than 2.6.23

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Date:	Tue, 29 Apr 2008 09:10:36 -0400
From:	"Ross Biro" <rossb@...gle.com>
To:	linux-mm@...ck.org, lkml <linux-kernel@...r.kernel.org>
Subject: Page Faults slower in 2.6.25-rc9 than 2.6.23

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.

    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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