Messages in this thread | | | Date | Wed, 26 Apr 2006 21:46:23 +0200 | From | Jens Axboe <> | Subject | Re: Lockless page cache test results |
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On Thu, Apr 27 2006, Nick Piggin wrote: > Jens Axboe wrote: > >Hi, > > > >Running a splice benchmark on a 4-way IPF box, I decided to give the > >lockless page cache patches from Nick a spin. I've attached the results > >as a png, it pretty much speaks for itself. > > > >The test in question splices a 1GiB file to a pipe and then splices that > >to some output. Normally that output would be something interesting, in > >this case it's simply /dev/null. So it tests the input side of things > >only, which is what I wanted to do here. To get adequate runtime, the > >operation is repeated a number of times (120 in this example). The > >benchmark does that number of loops with 1, 2, 3, and 4 clients each > >pinned to a private CPU. The pinning is mainly done for more stable > >results. > > Thanks Jens! > > It's interesting, single threaded performance is down a little. Is > this significant? In some other results you showed me with 3 splices > each running on their own file (ie. no tree_lock contention), lockless > looked slightly faster on the same machine.
I can't say for sure, as I haven't done enough of these runs to know for a fact if it's just a little fluctuation or actually statistically significant. The tests are quick to run, I'll do a series of single thread runs tomorrow to tell you.
> It could well be that the speculative get_page operation is naturally > a bit slower on Itanium CPUs -- there is a different mix of barriers, > reads, writes, etc. If only someone gave me an IPF system... ;)
I'll gladly trade the heat and noise generation of that beast with you :-)
I can do the same numbers on a 2-way em64t for comparison, that should get us a little better coverage.
> As you said, it would be nice to see how this goes when the other end > are 4 gigabit pipes or so... And then things like specweb and file > serving workloads.
Yes, for now I just consider the /dev/null splicing an extremely fast and extremely light weigth interconnect :-)
-- Jens Axboe
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