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Message-Id: <1270631267.2078.380.camel@ymzhang.sh.intel.com> Date: Wed, 07 Apr 2010 17:07:47 +0800 From: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Christoph Lameter <cl@...ux-foundation.org>, netdev <netdev@...r.kernel.org>, Tejun Heo <tj@...nel.org>, Pekka Enberg <penberg@...helsinki.fi>, alex.shi@...el.com, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Ma, Ling" <ling.ma@...el.com>, "Chen, Tim C" <tim.c.chen@...el.com>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: hackbench regression due to commit 9dfc6e68bfe6e On Wed, 2010-04-07 at 08:39 +0200, Eric Dumazet wrote: > Le mercredi 07 avril 2010 à 10:34 +0800, Zhang, Yanmin a écrit : > > > I collected retired instruction, dtlb miss and LLC miss. > > Below is data of LLC miss. > > > > Kernel 2.6.33: > > # Samples: 11639436896 LLC-load-misses > > # > > # Overhead Command Shared Object Symbol > > # ........ ............... ...................................................... ...... > > # > > 20.94% hackbench [kernel.kallsyms] [k] copy_user_generic_string > > 14.56% hackbench [kernel.kallsyms] [k] unix_stream_recvmsg > > 12.88% hackbench [kernel.kallsyms] [k] kfree > > 7.37% hackbench [kernel.kallsyms] [k] kmem_cache_free > > 7.18% hackbench [kernel.kallsyms] [k] kmem_cache_alloc_node > > 6.78% hackbench [kernel.kallsyms] [k] kfree_skb > > 6.27% hackbench [kernel.kallsyms] [k] __kmalloc_node_track_caller > > 2.73% hackbench [kernel.kallsyms] [k] __slab_free > > 2.21% hackbench [kernel.kallsyms] [k] get_partial_node > > 2.01% hackbench [kernel.kallsyms] [k] _raw_spin_lock > > 1.59% hackbench [kernel.kallsyms] [k] schedule > > 1.27% hackbench hackbench [.] receiver > > 0.99% hackbench libpthread-2.9.so [.] __read > > 0.87% hackbench [kernel.kallsyms] [k] unix_stream_sendmsg > > > > > > > > > > Kernel 2.6.34-rc3: > > # Samples: 13079611308 LLC-load-misses > > # > > # Overhead Command Shared Object Symbol > > # ........ ............... .................................................................... ...... > > # > > 18.55% hackbench [kernel.kallsyms] [k] copy_user_generic_str > > ing > > 13.19% hackbench [kernel.kallsyms] [k] unix_stream_recvmsg > > 11.62% hackbench [kernel.kallsyms] [k] kfree > > 8.54% hackbench [kernel.kallsyms] [k] kmem_cache_free > > 7.88% hackbench [kernel.kallsyms] [k] __kmalloc_node_track_ > > caller > > 6.54% hackbench [kernel.kallsyms] [k] kmem_cache_alloc_node > > 5.94% hackbench [kernel.kallsyms] [k] kfree_skb > > 3.48% hackbench [kernel.kallsyms] [k] __slab_free > > 2.15% hackbench [kernel.kallsyms] [k] _raw_spin_lock > > 1.83% hackbench [kernel.kallsyms] [k] schedule > > 1.82% hackbench [kernel.kallsyms] [k] get_partial_node > > 1.59% hackbench hackbench [.] receiver > > 1.37% hackbench libpthread-2.9.so [.] __read > > > > > > Please check values of /proc/sys/net/core/rmem_default > and /proc/sys/net/core/wmem_default on your machines. > > Their values can also change hackbench results, because increasing > wmem_default allows af_unix senders to consume much more skbs and stress > slab allocators (__slab_free), way beyond slub_min_order can tune them. > > When 2000 senders are running (and 2000 receivers), we might consume > something like 2000 * 100.000 bytes of kernel memory for skbs. TLB > trashing is expected, because all these skbs can span many 2MB pages. > Maybe some node imbalance happens too. It's a good pointer. rmem_default and wmem_default are about 116k on my machine. I changed them to 52K and it seems there is no improvement. > > > > You could try to boot your machine with less ram per node and check : > > # cat /proc/buddyinfo > Node 0, zone DMA 2 1 2 2 1 1 1 0 1 1 3 > Node 0, zone DMA32 219 298 143 584 145 57 44 41 31 26 517 > Node 1, zone DMA32 4 1 17 1 0 3 2 2 2 2 123 > Node 1, zone Normal 126 169 83 8 7 5 59 59 49 28 459 > > > One experiment on your Nehalem machine would be to change hackbench so > that each group (20 senders/ 20 receivers) run on a particular NUMA > node. I expect process scheduler to work well in scheduling different groups to different nodes. I suspected dynamic percpu data didn't take care of NUMA, but kernel dump shows it does take care of NUMA. > > x86info -c -> > > CPU #1 > EFamily: 0 EModel: 1 Family: 6 Model: 26 Stepping: 5 > CPU Model: Core i7 (Nehalem) > Processor name string: Intel(R) Xeon(R) CPU X5570 @ 2.93GHz > Type: 0 (Original OEM) Brand: 0 (Unsupported) > Number of cores per physical package=8 > Number of logical processors per socket=16 > Number of logical processors per core=2 > APIC ID: 0x10 Package: 0 Core: 1 SMT ID 0 > Cache info > L1 Instruction cache: 32KB, 4-way associative. 64 byte line size. > L1 Data cache: 32KB, 8-way associative. 64 byte line size. > L2 (MLC): 256KB, 8-way associative. 64 byte line size. > TLB info > Data TLB: 4KB pages, 4-way associative, 64 entries > 64 byte prefetching. > Found unknown cache descriptors: 55 5a b2 ca e4 > > -- 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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