Date: Tue, 24 Apr 2012 23:14:15 +0400 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: freebsd-current@freebsd.org, freebsd-performance@freebsd.org Subject: pmap and mtx scalability problem Message-ID: <20120424191415.GE76983@zxy.spb.ru>
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I treid make -j 30 build{world,kernel} (latest -CURRENT) on 24-core machine and see poor
scalability of pmap/mtx -- more then 50% cpu spend on system time.
pmcstat:
@ CPU_CLK_UNHALTED_CORE [194841 samples]
42.65% [83102] _mtx_lock_sleep @ /boot/kernel/kernel
40.97% [34051] pmap_enter
100.0% [34051] vm_fault_hold
100.0% [34051] trap_pfault
30.40% [25262] vm_page_activate
100.0% [25262] vm_fault_hold
100.0% [25262] trap_pfault
18.41% [15300] vm_pageq_remove
73.63% [11266] vm_page_free_toq
70.69% [7964] vm_object_terminate
29.31% [3302] vm_object_page_remove
26.37% [4034] vm_fault_hold
100.0% [4034] trap_pfault
make -j 8:
15.44% [10740] _mtx_lock_sleep @ /boot/kernel/kernel
38.77% [4164] pmap_enter
99.93% [4161] vm_fault_hold
100.0% [4161] trap_pfault
00.07% [3] kmem_back
100.0% [3] kmem_malloc
27.98% [3005] vm_page_activate
100.0% [3005] vm_fault_hold
100.0% [3005] trap_pfault
20.64% [2217] vm_pageq_remove
64.73% [1435] vm_page_free_toq
63.41% [910] vm_object_terminate
make -j 4
06.86% [4222] pagezero @ /boot/kernel/kernel
98.39% [4154] trap_pfault
100.0% [4154] trap
01.11% [47] vm_fault_hold
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