Date: Tue, 24 Apr 2012 21:27:30 +0200 From: "K. Macy" <kmacy@freebsd.org> To: Slawa Olhovchenkov <slw@zxy.spb.ru> Cc: freebsd-performance@freebsd.org, freebsd-current@freebsd.org Subject: Re: pmap and mtx scalability problem Message-ID: <CAHM0Q_PEe18-4yfrHPujUWxsvWTUuP2-0QvJtWOh2f=igjqh=A@mail.gmail.com> In-Reply-To: <20120424191415.GE76983@zxy.spb.ru> References: <20120424191415.GE76983@zxy.spb.ru>
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Known problem. There is an open disagreement about how to improve the
granularity of locking in pmap.
-Kip
On Tue, Apr 24, 2012 at 9:14 PM, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote:
> 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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