2 x quad-core system is slower that 2 x dual core on FreeBSD
max at love2party.net
Thu Nov 22 00:13:57 PST 2007
On Tuesday 20 November 2007, Kris Kennaway wrote:
> Kris Kennaway wrote:
> > Kris Kennaway wrote:
> >> In the meantime there is unfortunately not a lot that can be done,
> >> AFAICT. There is one hack that I will send you later but it is not
> >> likely to help much. I will also think about how to track down the
> >> cause of the contention further (the profiling trace only shows that
> >> it comes mostly from vget/vput but doesn't show where these are
> >> called from).
> > Actually this patch might help. It doesn't replace lockmgr but it
> > does fix a silly thundering herd behaviour. It probably needs some
> > adjustment to get it to apply cleanly (it is about 7 months old), and
> > I apparently stopped using it because I ran into deadlocks. It might
> > be stable enough to at least see how much it helps.
> > Set the vfs.lookup_shared=1 sysctl to enable the other half of the
> > patch.
> > Kris
> Try this one instead, it applies to HEAD. You'll need to manually
> enter the paths though because of how p4 mangles diffs.
I rolled a tiny, simple, possibly braindamaged benchmark (but then again
php code tends to be braindamaged): test.php includes 1000 different,
essential empty files and is strated over and over from a shell script
which counts the runs completed within 60seconds. 1-8,128 scripts are
started in parallel.
On a 2x dual Opteron running amd64 I get:
stock RELENG_7 w/o patch ULE:
jobs sum runs gain
1 617 1
2 784 1.27
3 939 1.52
4 1015 1.65
5 658 1.07
6 642 1.04
7 666 1.08
8 696 1.13
128 726 1.18
RELENG_7 patched ULE vfs.lookup_shared=1:
jobs sum runs gain
1 637 1
2 784 1.23
3 973 1.53
4 1104 1.73
5 708 1.11
6 733 1.15
7 776 1.22
8 840 1.32
128 936 1.47
So there is still a lot of room for improvement here. I'll rebuild with
lock profiling tomorrow and see what I can gather. Anything you'd like
to see in particular?
/"\ Best regards, | mlaier at freebsd.org
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