Le mercredi 07 avril 2010 à 10:34 +0800, Zhang, Yanmin a écrit :
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.
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.
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
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