Messages in this thread | | | Date | Fri, 12 Dec 2008 06:50:51 +0100 | From | Nick Piggin <> | Subject | Re: [rfc][patch] SLQB slab allocator |
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On Fri, Dec 12, 2008 at 06:38:26AM +0100, Eric Dumazet wrote: > Nick Piggin a écrit : > > I'm going to continue working on this as I get time, and I plan to soon ask > > to have it merged. It would be great if people could comment or test it. > > > > It seems really good, but will need some hours to review :) > > Minor nit : You spelled Qeued instead of Queued in init/Kconfig > > +config SLQB > + bool "SLQB (Qeued allocator)"
OK, thanks.
> One of the problem I see with SLAB & SLUB is the irq masking stuff. > Some (many ???) kmem_cache are only used in process context, I see no point of > disabling irqs for them.
That's a very good point actually, and something I want to look at...
I'm thinking it will make most sense to provide a kmem_cache_alloc/free_irqsafe for callers who either don't do any interrupt context allocations, or already have irqs off (another slab flag will just add another branch in the fastpaths).
And then also a kmalloc/kfree_irqsoff for code which already has irqs off.
That's something which benefit all slab allocators roughly equally, so at the moment I'm concentrating on the core code. But it's a very good idea.
> I tested your patch on my 8 ways HP BL460c G1, on top > on my last patch serie. (linux-2.6, not net-next-2.6) > > # time ./socketallocbench > > real 0m1.300s > user 0m0.078s > sys 0m1.207s > # time ./socketallocbench -n 8 > > real 0m1.686s > user 0m0.614s > sys 0m12.737s > > So no bad effect (same than SLUB).
Cool, thanks.
> For the record, SLAB is really really bad for this workload > > PU: Core 2, speed 3000.1 MHz (estimated) > Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100 > 000 > samples cum. samples % cum. % symbol name > 136537 136537 10.8300 10.8300 kmem_cache_alloc > 129380 265917 10.2623 21.0924 tcp_close > 79696 345613 6.3214 27.4138 tcp_v4_init_sock > 73873 419486 5.8596 33.2733 tcp_v4_destroy_sock > 63436 482922 5.0317 38.3050 sysenter_past_esp > 62140 545062 4.9289 43.2339 inet_csk_destroy_sock > 56565 601627 4.4867 47.7206 kmem_cache_free > 40430 642057 3.2069 50.9275 __percpu_counter_add > 35742 677799 2.8350 53.7626 init_timer > 35611 713410 2.8246 56.5872 copy_from_user > 21616 735026 1.7146 58.3018 d_alloc > 20821 755847 1.6515 59.9533 alloc_inode > 19645 775492 1.5582 61.5115 alloc_fd > 18935 794427 1.5019 63.0134 __fput > 18922 813349 1.5009 64.5143 inet_create > 18919 832268 1.5006 66.0149 sys_close > 16074 848342 1.2750 67.2899 release_sock > 15337 863679 1.2165 68.5064 lock_sock_nested > 15172 878851 1.2034 69.7099 sock_init_data > 14196 893047 1.1260 70.8359 fd_install > 13677 906724 1.0849 71.9207 drop_file_write_access > 13195 919919 1.0466 72.9673 dput > 12768 932687 1.0127 73.9801 inotify_d_instantiate > 11404 944091 0.9046 74.8846 init_waitqueue_head > 11228 955319 0.8906 75.7752 sysenter_do_call > 11213 966532 0.8894 76.6647 local_bh_enable_ip > 10948 977480 0.8684 77.5330 __sock_create > 10912 988392 0.8655 78.3986 local_bh_enable > 10665 999057 0.8459 79.2445 __new_inode > 10579 1009636 0.8391 80.0836 inet_release > 9665 1019301 0.7666 80.8503 iput_single > 9545 1028846 0.7571 81.6074 fput > 7950 1036796 0.6306 82.2379 sock_release > 7236 1044032 0.5740 82.8119 local_bh_disable > > > We can see most of the time is taken by the memset() to clear object, > then irq masking stuff...
Yep, it's difficult to make the local alloc/free fastpath much more optimal as-is.
Is SLAB still bad at the test with the slab-rcu patch in place? SLAB has a pretty optimal fastpath as well, although if its queues start overflowing, it can run into contention quite easily.
> > c0281e10 <kmem_cache_alloc>: /* kmem_cache_alloc total: 140659 10.8277 */
I guess you're compiling with -Os? I find gcc can pack the fastpath much better with -O2, and actually decrease the effective icache footprint size even if the total text size increases...
> 2414 0.1858 :c0281e10: push %ebp > 7 5.4e-04 :c0281e11: mov %esp,%ebp > :c0281e13: push %edi > 1454 0.1119 :c0281e14: push %esi > 310 0.0239 :c0281e15: mov %eax,%esi > :c0281e17: push %ebx > 368 0.0283 :c0281e18: sub $0x10,%esp > 949 0.0731 :c0281e1b: mov %edx,-0x18(%ebp) > 383 0.0295 :c0281e1e: mov 0x4(%ebp),%eax > 1189 0.0915 :c0281e21: mov %eax,-0x14(%ebp) > 1240 0.0955 :c0281e24: jmp c0281e6e <kmem_cache_alloc+0x5e> > :c0281e26: lea 0x0(%esi),%esi > :c0281e29: lea 0x0(%edi,%eiz,1),%edi > 1188 0.0915 :c0281e30: mov 0x10(%esi),%eax > :c0281e33: mov (%edx,%eax,1),%eax > 1483 0.1142 :c0281e36: decl (%ebx) > 898 0.0691 :c0281e38: mov %eax,0x4(%ebx) > 586 0.0451 :c0281e3b: mov %edx,-0x1c(%ebp) > 1 7.7e-05 :c0281e3e: pushl -0x10(%ebp) > 1226 0.0944 :c0281e41: popf > 26385 2.0311 :c0281e42: testl $0x210d00,(%esi) > 1188 0.0915 :c0281e48: je c0281ef8 <kmem_cache_alloc+0xe8> > :c0281e4e: mov -0x1c(%ebp),%eax > :c0281e51: test %eax,%eax > :c0281e53: je c0281ef8 <kmem_cache_alloc+0xe8> > :c0281e59: mov -0x14(%ebp),%ecx > :c0281e5c: mov -0x1c(%ebp),%edx > :c0281e5f: mov %esi,%eax > :c0281e61: call c0280d60 <alloc_debug_processing> > :c0281e66: test %eax,%eax > :c0281e68: jne c0281ef8 <kmem_cache_alloc+0xe8> > 1205 0.0928 :c0281e6e: pushf > 4888 0.3763 :c0281e6f: popl -0x10(%ebp) > 319 0.0246 :c0281e72: cli > 5975 0.4599 :c0281e73: nop > :c0281e74: lea 0x0(%esi,%eiz,1),%esi > :c0281e78: mov %fs:0xc068d004,%eax > 1166 0.0898 :c0281e7e: mov 0x38(%esi,%eax,4),%ebx > 26 0.0020 :c0281e82: mov 0x4(%ebx),%edx > 662 0.0510 :c0281e85: test %edx,%edx > :c0281e87: jne c0281e30 <kmem_cache_alloc+0x20> > :c0281e89: mov 0xc(%ebx),%eax > :c0281e8c: test %eax,%eax > :c0281e8e: jne c0281ec8 <kmem_cache_alloc+0xb8> > :c0281e90: mov %ebx,%edx > :c0281e92: mov %esi,%eax > :c0281e94: call c0280010 <__cache_list_get_page> > :c0281e99: mov %eax,%edx > :c0281e9b: test %eax,%eax > :c0281e9d: jne c0281f31 <kmem_cache_alloc+0x121> > :c0281ea3: mov $0xffffffff,%ecx > 1 7.7e-05 :c0281ea8: mov -0x18(%ebp),%edx > :c0281eab: mov %esi,%eax > :c0281ead: call c02815a0 <__slab_alloc_page> > :c0281eb2: test %eax,%eax > :c0281eb4: jne c0281e78 <kmem_cache_alloc+0x68> > :c0281eb6: movl $0x0,-0x1c(%ebp) > :c0281ebd: jmp c0281e3e <kmem_cache_alloc+0x2e> > :c0281ec2: lea 0x0(%esi),%esi > :c0281ec8: mov %esi,%eax > :c0281eca: mov %ebx,%edx > :c0281ecc: call c0280240 <claim_remote_free_list> > :c0281ed1: mov 0x4(%esi),%eax > :c0281ed4: shl $0x2,%eax > :c0281ed7: cmp %eax,(%ebx) > :c0281ed9: ja c0281f48 <kmem_cache_alloc+0x138> > :c0281edb: mov 0x4(%ebx),%edx > :c0281ede: mov %edx,-0x1c(%ebp) > :c0281ee1: test %edx,%edx > :c0281ee3: je c0281e90 <kmem_cache_alloc+0x80> > :c0281ee5: mov 0x10(%esi),%eax > :c0281ee8: mov (%edx,%eax,1),%eax > :c0281eeb: decl (%ebx) > :c0281eed: mov %eax,0x4(%ebx) > :c0281ef0: jmp c0281e3e <kmem_cache_alloc+0x2e> > > :c0281ef5: lea 0x0(%esi),%esi > 1261 0.0971 :c0281ef8: cmpw $0x0,-0x18(%ebp) > 957 0.0737 :c0281efd: jns c0281f26 <kmem_cache_alloc+0x116> > 627 0.0483 :c0281eff: mov -0x1c(%ebp),%eax > :c0281f02: test %eax,%eax > :c0281f04: je c0281f26 <kmem_cache_alloc+0x116> > 82 0.0063 :c0281f06: mov 0xc(%esi),%esi > 2 1.5e-04 :c0281f09: mov -0x1c(%ebp),%ebx > 527 0.0406 :c0281f0c: mov %esi,%ecx > :c0281f0e: mov %ebx,%edi > 86 0.0066 :c0281f10: shr $0x2,%ecx > 602 0.0463 :c0281f13: xor %eax,%eax > 1 7.7e-05 :c0281f15: mov %esi,%edx > 74845 5.7614 :c0281f17: rep stos %eax,%es:(%edi) > 1170 0.0901 :c0281f19: test $0x2,%dl > 2 1.5e-04 :c0281f1c: je c0281f20 <kmem_cache_alloc+0x110> > :c0281f1e: stos %ax,%es:(%edi) > 600 0.0462 :c0281f20: test $0x1,%dl > :c0281f23: je c0281f26 <kmem_cache_alloc+0x116> > :c0281f25: stos %al,%es:(%edi) > 1171 0.0901 :c0281f26: mov -0x1c(%ebp),%eax > 199 0.0153 :c0281f29: add $0x10,%esp > :c0281f2c: pop %ebx > 2 1.5e-04 :c0281f2d: pop %esi > 1215 0.0935 :c0281f2e: pop %edi > 548 0.0422 :c0281f2f: leave > 1251 0.0963 :c0281f30: ret > :c0281f31: mov 0x10(%edx),%ecx > :c0281f34: mov %ecx,-0x1c(%ebp) > :c0281f37: mov 0x10(%esi),%eax > :c0281f3a: mov (%ecx,%eax,1),%eax > :c0281f3d: mov %eax,0x10(%edx) > :c0281f40: jmp c0281e3e <kmem_cache_alloc+0x2e> > :c0281f45: lea 0x0(%esi),%esi > :c0281f48: mov %ebx,%edx > :c0281f4a: mov %esi,%eax > :c0281f4c: call c02811d0 <flush_free_list> > :c0281f51: jmp c0281edb <kmem_cache_alloc+0xcb> > :c0281f53: lea 0x0(%esi),%esi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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