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Message-ID: <20070822011225.GA4124@Krystal> Date: Tue, 21 Aug 2007 21:12:25 -0400 From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> To: Christoph Lameter <clameter@....com> Cc: Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, mingo@...hat.com Subject: Re: [PATCH] SLUB use cmpxchg_local * Christoph Lameter (clameter@....com) wrote: > Ok. Measurements vs. simple cmpxchg on a Intel(R) Pentium(R) 4 CPU 3.20GHz > (hyperthreading enabled). Test run with your module show only minor > performance improvements and lots of regressions. So we must have > cmpxchg_local to see any improvements? Some kind of a recent optimization > of cmpxchg performance that we do not see on older cpus? > I did not expect the cmpxchg with LOCK prefix to be faster than irq save/restore. You will need to run these tests using cmpxchg_local to see an improvement. Mathieu > > Code of kmem_cache_alloc (to show you that there are no debug options on): > > Dump of assembler code for function kmem_cache_alloc: > 0x4015cfa9 <kmem_cache_alloc+0>: push %ebp > 0x4015cfaa <kmem_cache_alloc+1>: mov %esp,%ebp > 0x4015cfac <kmem_cache_alloc+3>: push %edi > 0x4015cfad <kmem_cache_alloc+4>: push %esi > 0x4015cfae <kmem_cache_alloc+5>: push %ebx > 0x4015cfaf <kmem_cache_alloc+6>: sub $0x10,%esp > 0x4015cfb2 <kmem_cache_alloc+9>: mov %eax,%esi > 0x4015cfb4 <kmem_cache_alloc+11>: mov %edx,0xffffffe8(%ebp) > 0x4015cfb7 <kmem_cache_alloc+14>: mov 0x4(%ebp),%eax > 0x4015cfba <kmem_cache_alloc+17>: mov %eax,0xfffffff0(%ebp) > 0x4015cfbd <kmem_cache_alloc+20>: mov %fs:0x404af008,%eax > 0x4015cfc3 <kmem_cache_alloc+26>: mov 0x90(%esi,%eax,4),%edi > 0x4015cfca <kmem_cache_alloc+33>: mov (%edi),%ecx > 0x4015cfcc <kmem_cache_alloc+35>: test %ecx,%ecx > 0x4015cfce <kmem_cache_alloc+37>: je 0x4015d00a <kmem_cache_alloc+97> > 0x4015cfd0 <kmem_cache_alloc+39>: mov 0xc(%edi),%eax > 0x4015cfd3 <kmem_cache_alloc+42>: mov (%ecx,%eax,4),%eax > 0x4015cfd6 <kmem_cache_alloc+45>: mov %eax,%edx > 0x4015cfd8 <kmem_cache_alloc+47>: mov %ecx,%eax > 0x4015cfda <kmem_cache_alloc+49>: lock cmpxchg %edx,(%edi) > 0x4015cfde <kmem_cache_alloc+53>: mov %eax,%ebx > 0x4015cfe0 <kmem_cache_alloc+55>: cmp %ecx,%eax > 0x4015cfe2 <kmem_cache_alloc+57>: jne 0x4015cfbd <kmem_cache_alloc+20> > 0x4015cfe4 <kmem_cache_alloc+59>: cmpw $0x0,0xffffffe8(%ebp) > 0x4015cfe9 <kmem_cache_alloc+64>: jns 0x4015d006 <kmem_cache_alloc+93> > 0x4015cfeb <kmem_cache_alloc+66>: mov 0x10(%edi),%edx > 0x4015cfee <kmem_cache_alloc+69>: xor %eax,%eax > 0x4015cff0 <kmem_cache_alloc+71>: mov %edx,%ecx > 0x4015cff2 <kmem_cache_alloc+73>: shr $0x2,%ecx > 0x4015cff5 <kmem_cache_alloc+76>: mov %ebx,%edi > > Base > > 1. Kmalloc: Repeatedly allocate then free test > 10000 times kmalloc(8) -> 332 cycles kfree -> 422 cycles > 10000 times kmalloc(16) -> 218 cycles kfree -> 360 cycles > 10000 times kmalloc(32) -> 214 cycles kfree -> 368 cycles > 10000 times kmalloc(64) -> 244 cycles kfree -> 390 cycles > 10000 times kmalloc(128) -> 320 cycles kfree -> 417 cycles > 10000 times kmalloc(256) -> 438 cycles kfree -> 550 cycles > 10000 times kmalloc(512) -> 527 cycles kfree -> 626 cycles > 10000 times kmalloc(1024) -> 678 cycles kfree -> 775 cycles > 10000 times kmalloc(2048) -> 748 cycles kfree -> 822 cycles > 10000 times kmalloc(4096) -> 641 cycles kfree -> 650 cycles > 10000 times kmalloc(8192) -> 741 cycles kfree -> 817 cycles > 10000 times kmalloc(16384) -> 872 cycles kfree -> 927 cycles > 2. Kmalloc: alloc/free test > 10000 times kmalloc(8)/kfree -> 332 cycles > 10000 times kmalloc(16)/kfree -> 327 cycles > 10000 times kmalloc(32)/kfree -> 323 cycles > 10000 times kmalloc(64)/kfree -> 320 cycles > 10000 times kmalloc(128)/kfree -> 320 cycles > 10000 times kmalloc(256)/kfree -> 333 cycles > 10000 times kmalloc(512)/kfree -> 332 cycles > 10000 times kmalloc(1024)/kfree -> 330 cycles > 10000 times kmalloc(2048)/kfree -> 334 cycles > 10000 times kmalloc(4096)/kfree -> 674 cycles > 10000 times kmalloc(8192)/kfree -> 1155 cycles > 10000 times kmalloc(16384)/kfree -> 1226 cycles > > Slub cmpxchg. > > 1. Kmalloc: Repeatedly allocate then free test > 10000 times kmalloc(8) -> 296 cycles kfree -> 515 cycles > 10000 times kmalloc(16) -> 193 cycles kfree -> 412 cycles > 10000 times kmalloc(32) -> 188 cycles kfree -> 422 cycles > 10000 times kmalloc(64) -> 222 cycles kfree -> 441 cycles > 10000 times kmalloc(128) -> 292 cycles kfree -> 476 cycles > 10000 times kmalloc(256) -> 414 cycles kfree -> 589 cycles > 10000 times kmalloc(512) -> 513 cycles kfree -> 673 cycles > 10000 times kmalloc(1024) -> 694 cycles kfree -> 825 cycles > 10000 times kmalloc(2048) -> 739 cycles kfree -> 878 cycles > 10000 times kmalloc(4096) -> 636 cycles kfree -> 653 cycles > 10000 times kmalloc(8192) -> 715 cycles kfree -> 799 cycles > 10000 times kmalloc(16384) -> 855 cycles kfree -> 927 cycles > 2. Kmalloc: alloc/free test > 10000 times kmalloc(8)/kfree -> 354 cycles > 10000 times kmalloc(16)/kfree -> 336 cycles > 10000 times kmalloc(32)/kfree -> 335 cycles > 10000 times kmalloc(64)/kfree -> 337 cycles > 10000 times kmalloc(128)/kfree -> 337 cycles > 10000 times kmalloc(256)/kfree -> 355 cycles > 10000 times kmalloc(512)/kfree -> 354 cycles > 10000 times kmalloc(1024)/kfree -> 337 cycles > 10000 times kmalloc(2048)/kfree -> 339 cycles > 10000 times kmalloc(4096)/kfree -> 674 cycles > 10000 times kmalloc(8192)/kfree -> 1128 cycles > 10000 times kmalloc(16384)/kfree -> 1240 cycles > > -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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