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Subject2.2.17pre10 pauses fixed by Andrea's VM-global-patch-1
While running the "brutal" (-- Alan Cox) Cerberus test suite on a
2.2.17pre10 kernel, we've been seeing pauses of from five to twenty
seconds every two minutes or so. As best I can tell from SysReq, when
the kernel pauses, it's spending time in shrink_mmap(). When pauses
occur, free RAM is down to about 1M; but it's not a true OOM, since
there's always lots of free swap space. (Cerberus scales its memory
usage to avoid filling swap.)

Good News: The pauses are *almost* completely gone after applying
Andrea's patch entitled "VM-global-patch-1". The kernel still pauses,
but only very occasionally, and for no more than two to four seconds;
and even during the pauses, interactive performance is reasonable.
According to Jason Collins, creator of Cerberus, it's at least as good
as any previous 2.2.x when subjected to a Cerberus attack.

Thanks, Andrea!

PS: Anyone who wants to stress the VM, I recommend trying Cerberus
as part of your testing mix. Get it from SourceForge:
<URL:https://sourceforge.net/projects/va-ctcs/>

Testing Details:
Kernel: 2.2.17pre10
Config: SMP, 2G, NFS root
Hardware: Intel Lancewood, two P3s, 512M RAM, DAC960 RAID
Relevant Patches:
Dave/Trond/Neil's NFS merge
Andrea's VM-global-patch-1
Andrea's BIGMEM
Solar Designer's security
Probably Irrelevant Patches:
Rik's fair share scheduler (but disabled at the time)
Andre Hedrick's IDE
Mingo's RAID
VA's E820 memory probe
Backport of 2.4's AGP driver

--
Chip Salzenberg - a.k.a. - <chip@valinux.com>
"I wanted to play hopscotch with the impenetrable mystery of existence,
but he stepped in a wormhole and had to go in early." // MST3K
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