Messages in this thread | | | Date | Wed, 17 Dec 2008 08:09:54 +0100 | From | Nick Piggin <> | Subject | Re: [rfc][patch] SLQB slab allocator |
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On Wed, Dec 17, 2008 at 04:01:06PM +0900, MinChan Kim wrote: > On Wed, Dec 17, 2008 at 3:42 PM, Nick Piggin <npiggin@suse.de> wrote: > >> Below is average for ten time test. > >> > >> slab : > >> user : 2376.484, system : 192.616 elapsed : 12:22.0 > >> slub : > >> user : 2378.439, system : 194.989 elapsed : 12:22.4 > >> slqb : > >> user : 2380.556, system : 194.801 elapsed : 12:23.0 > >> > >> so, slqb is rather slow although it is a big difference. > >> Interestingly, slqb consumes less time than slub in system. > > > > Thanks, interesting test. kbuild is not very slab allocator intensive, > > Let me know what is popular benchmark program in slab allocator. > I will try with it. :)
That's not to say it is a bad benchmark :) If it shows up a difference and is a useful workload like kbuild, then it is a good benchmark.
Allocator changes tend to show up more when there is a lot of network or disk IO happening. But it is good to see other tets too, so any numbers you get are welcome.
> > so I hadn't thought of trying it. Possibly the object cacheline layout > > of longer lived allocations changes the behaviour (increased user time > > could indicate that). > > What mean "object cacheline layout of loger lived allocations" ?
For example, different allocation schemes will alter the chances of getting different ways (colours), or false sharing. SLUB and SLQB for example allow as fine as 8 byte allocation granularity wheras SLAB goes down to 32 bytes, so small objects *could* be more prone to false sharing. I don't know for sure at this stage, just guessing ;)
The difference doesn't show up significantly on my system, so profiling doesn't reveal anything (I guess even on your system it would be difficult to profile because it is not a huge difference).
> > I've been making a few changes to that, and hopefully slqb is slightly > > improved now (the margin is much closer, seems within the noise with > > SLUB on my NUMA opteron now, although that's a very different system). > > > > The biggest bug I fixed was that the NUMA path wasn't being taken in > > kmem_cache_free on NUMA systems (oops), but that wouldn't change your > > result. But I did make some other changes too, eg in prefetching. > > OK. I will review and test your new patch in my machine.
Thanks! Code style and comments should be improved quite a bit now.
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