From: Avi Kivity <avi@redhat.com>
To: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v2 19/22] KVM: MMU: lockless walking shadow page table
Date: Wed, 29 Jun 2011 15:27:58 +0300 [thread overview]
Message-ID: <4E0B1A4E.2030301@redhat.com> (raw)
In-Reply-To: <4E0B1A75.4070705@cn.fujitsu.com>
On 06/29/2011 03:28 PM, Xiao Guangrong wrote:
> On 06/29/2011 08:18 PM, Avi Kivity wrote:
> > On 06/29/2011 02:50 PM, Xiao Guangrong wrote:
> >> >> >
> >> >> > I think we should do this unconditionally. The cost of ping-ponging the shared cache line containing reader_counter will increase with large smp counts. On the other hand, zap_page is very rare, so it can be a little slower. Also, less code paths = easier to understand.
> >> >> >
> >> >>
> >> >> On soft mmu, zap_page is very frequently, it can cause performance regression in my test.
> >> >
> >> > Any idea what the cause of the regression is? It seems to me that simply deferring freeing shouldn't have a large impact.
> >> >
> >>
> >> I guess it is because the page is freed too frequently, i have done the test, it shows
> >> about 3219 pages is freed per second
> >>
> >> Kernbench performance comparing:
> >>
> >> the origin way: 3m27.723
> >> free all shadow page in rcu context: 3m30.519
> >
> > I don't recall seeing such a high free rate. Who is doing all this zapping?
> >
> > You may be able to find out with the function tracer + call graph.
> >
>
> I looked into it before, it is caused by "write flood" detected, i also noticed
> some pages are zapped and allocation again and again, maybe we need to improve
> the algorithm of detecting "write flood".
Ok. Let's drop the two paths, and put this improvement on the TODO instead.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-06-29 12:28 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-22 14:27 [PATCH v2 0/22] KVM: optimize for MMIO handled Xiao Guangrong
2011-06-22 14:28 ` [PATCH v2 01/22] KVM: MMU: fix walking shadow page table Xiao Guangrong
2011-06-22 17:13 ` Marcelo Tosatti
2011-06-23 2:05 ` Xiao Guangrong
2011-06-27 6:35 ` Xiao Guangrong
2011-06-22 14:28 ` [PATCH v2 02/22] KVM: MMU: do not update slot bitmap if spte is nonpresent Xiao Guangrong
2011-06-22 14:29 ` [PATCH v2 03/22] KVM: x86: fix broken read emulation spans a page boundary Xiao Guangrong
2011-06-29 8:21 ` Avi Kivity
2011-06-29 10:53 ` Xiao Guangrong
2011-06-29 11:19 ` Avi Kivity
2011-06-22 14:29 ` [PATCH v2 04/22] KVM: x86: introduce vcpu_gva_to_gpa to cleanup the code Xiao Guangrong
2011-06-29 8:24 ` Avi Kivity
2011-06-29 10:56 ` Xiao Guangrong
2011-06-29 11:09 ` Avi Kivity
2011-06-29 11:26 ` Xiao Guangrong
2011-06-29 11:26 ` Avi Kivity
2011-06-29 11:48 ` Gleb Natapov
2011-06-22 14:30 ` [PATCH v2 05/22] KVM: x86: abstract the operation for read/write emulation Xiao Guangrong
2011-06-29 8:37 ` Avi Kivity
2011-06-29 10:59 ` Xiao Guangrong
2011-06-22 14:30 ` [PATCH v2 06/22] KVM: x86: cleanup the code of " Xiao Guangrong
2011-06-22 14:31 ` [PATCH v2 07/22] KVM: MMU: cache mmio info on page fault path Xiao Guangrong
2011-06-29 8:48 ` Avi Kivity
2011-06-29 11:09 ` Xiao Guangrong
2011-06-29 11:10 ` Avi Kivity
2011-06-22 14:31 ` [PATCH v2 08/22] KVM: MMU: optimize to handle dirty bit Xiao Guangrong
2011-06-22 14:31 ` [PATCH v2 09/22] KVM: MMU: cleanup for FNAME(fetch) Xiao Guangrong
2011-06-22 14:32 ` [PATCH v2 10/22] KVM: MMU: rename 'pt_write' to 'emulate' Xiao Guangrong
2011-06-22 14:32 ` [PATCH v2 11/22] KVM: MMU: count used shadow pages on prepareing path Xiao Guangrong
2011-06-22 14:32 ` [PATCH v2 12/22] KVM: MMU: split kvm_mmu_free_page Xiao Guangrong
2011-06-22 14:33 ` [PATCH v2 13/22] KVM: MMU: remove bypass_guest_pf Xiao Guangrong
2011-06-22 14:33 ` [PATCH v2 14/22] KVM: MMU: filter out the mmio pfn from the fault pfn Xiao Guangrong
2011-06-22 14:34 ` [PATCH v2 15/22] KVM: MMU: abstract some functions to handle " Xiao Guangrong
2011-06-22 14:34 ` [PATCH v2 16/22] KVM: MMU: introduce the rules to modify shadow page table Xiao Guangrong
2011-06-22 14:34 ` [PATCH v2 17/22] KVM: MMU: clean up spte updating and clearing Xiao Guangrong
2011-06-22 14:35 ` [PATCH 18/22] KVM: MMU: do not need atomicly to set/clear spte Xiao Guangrong
2011-06-22 14:35 ` [PATCH v2 19/22] KVM: MMU: lockless walking shadow page table Xiao Guangrong
2011-06-29 9:16 ` Avi Kivity
2011-06-29 11:16 ` Xiao Guangrong
2011-06-29 11:18 ` Avi Kivity
2011-06-29 11:50 ` Xiao Guangrong
2011-06-29 12:18 ` Avi Kivity
2011-06-29 12:28 ` Xiao Guangrong
2011-06-29 12:27 ` Avi Kivity [this message]
2011-06-29 12:39 ` Xiao Guangrong
2011-06-29 13:01 ` Avi Kivity
2011-06-29 13:05 ` Xiao Guangrong
2011-06-22 14:35 ` [PATCH v2 20/22] KVM: MMU: reorganize struct kvm_shadow_walk_iterator Xiao Guangrong
2011-06-22 14:36 ` [PATCH v2 21/22] KVM: MMU: mmio page fault support Xiao Guangrong
2011-06-22 21:59 ` Marcelo Tosatti
2011-06-23 3:19 ` Xiao Guangrong
2011-06-23 6:40 ` Xiao Guangrong
2011-06-23 14:21 ` Marcelo Tosatti
2011-06-23 17:55 ` Xiao Guangrong
2011-06-23 20:13 ` Marcelo Tosatti
2011-06-24 2:04 ` Xiao Guangrong
2011-06-26 8:42 ` Avi Kivity
2011-06-27 11:00 ` [PATCH v3 " Xiao Guangrong
2011-06-29 9:22 ` [PATCH v2 " Avi Kivity
2011-06-29 12:28 ` Xiao Guangrong
2011-06-22 14:36 ` [PATCH v2 22/22] KVM: MMU: trace mmio page fault Xiao Guangrong
2011-06-29 9:23 ` [PATCH v2 0/22] KVM: optimize for MMIO handled Avi Kivity
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