On Tue, Apr 12, 2016 at 09:24:34AM +0200, Jesper Dangaard Brouer wrote: > On Tue, 12 Apr 2016 13:51:06 +0900 > js1304@xxxxxxxxx wrote: > > > From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > > > To check whther free objects exist or not precisely, we need to grab a > ^^^^^^ > (spelling) Will fix. > > lock. But, accuracy isn't that important because race window would be > > even small and if there is too much free object, cache reaper would reap > > it. So, this patch makes the check for free object exisistence not to > ^^^^^^^^^^^ > (spelling) Ditto. > > > hold a lock. This will reduce lock contention in heavily allocation case. > > > > Note that until now, n->shared can be freed during the processing by > > writing slabinfo, but, with some trick in this patch, we can access it > > freely within interrupt disabled period. > > > > Below is the result of concurrent allocation/free in slab allocation > > benchmark made by Christoph a long time ago. I make the output simpler. > > The number shows cycle count during alloc/free respectively so less is > > better. > > I cannot figure out which if Christoph's tests you are using. And I > even have a copy of his test here: > https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/slab_test.c I don't remember where I grab the source but it's same thing you have. But, my version has some modification for stable result. I do each test 50 times and get the average result. > I think you need to describe the test a bit better... Okay. I assume that relevant people (like as Christoph or you) can understand the result easily but it seems not. > Looking a long time at the output on my own system, I guess you are > showing results from the "Concurrent allocs". Then it would be > relevant how many CPUs your system have. Right. I'm doing the test with my 8 core i7-3770 CPU @ 3.40GHz. > It would also be relevant to mention that N=10000. And perhaps mention > that it means, e.g all CPUs do N=10000 alloc concurrently, synchronize > before doing N free concurrently. I'm doing the test with N=100000. > > > * Before > > Kmalloc N*alloc N*free(32): Average=248/966 > > Kmalloc N*alloc N*free(64): Average=261/949 > > Kmalloc N*alloc N*free(128): Average=314/1016 > > Kmalloc N*alloc N*free(256): Average=741/1061 > > Kmalloc N*alloc N*free(512): Average=1246/1152 > > Kmalloc N*alloc N*free(1024): Average=2437/1259 > > Kmalloc N*alloc N*free(2048): Average=4980/1800 > > Kmalloc N*alloc N*free(4096): Average=9000/2078 > > > > * After > > Kmalloc N*alloc N*free(32): Average=344/792 > > Kmalloc N*alloc N*free(64): Average=347/882 > > Kmalloc N*alloc N*free(128): Average=390/959 > > Kmalloc N*alloc N*free(256): Average=393/1067 > > Kmalloc N*alloc N*free(512): Average=683/1229 > > Kmalloc N*alloc N*free(1024): Average=1295/1325 > > Kmalloc N*alloc N*free(2048): Average=2513/1664 > > Kmalloc N*alloc N*free(4096): Average=4742/2172 > > > > It shows that allocation performance decreases for the object size up to > > 128 and it may be due to extra checks in cache_alloc_refill(). But, with > > considering improvement of free performance, net result looks the same. > > Result for other size class looks very promising, roughly, 50% performance > > improvement. > > Super nice performance boost. The numbers on my system are Thanks! > significantly smaller, but this is a before/after test and the absolute > numbers are not that important. > > Oh, maybe this was because I ran the test with SLUB... recompiling with > SLAB... and the results are comparable to your numbers (on my 8 core > i7-4790K CPU @ 4.00GHz) Okay. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>