From: Avi Kivity <avi@redhat.com>
To: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>,
kvm@vger.kernel.org
Subject: Re: [PATCH 3/4] KVM: Count the number of dirty pages for dirty logging
Date: Tue, 27 Dec 2011 17:06:47 +0200 [thread overview]
Message-ID: <4EF9DF07.2070208@redhat.com> (raw)
In-Reply-To: <20111228000322.33585bc7450433775326292e@gmail.com>
On 12/27/2011 05:03 PM, Takuya Yoshikawa wrote:
> Avi Kivity <avi@redhat.com> wrote:
>
> > > It should not be necessary, atomicity of updates to
> > > memslot->dirty_bitmap, because of RCU updates to the memslot pointer
> > > (note memslot = gfn_to_memslot(kvm, gfn); in mark_page_dirty).
> > >
> > > The order is:
> > >
> > > - update page data.
> > > - grab memslot pointer.
> > > - set page bit in memslot.
> > >
> >
> > What if both grab the same memslot pointer, but set different bits?
>
> (Sorry for my bad wording, that is what I wanted to explain.)
>
> There seems to be possible concurrent __set_bit()'s to the same word
> which will result in bit loss.
>
> I was thinking to change the kvm-unit-tests' dirty log test to write
> to two consecutive pages concurrently. Is this good for debugging this?
Yes, it already tests some concurrency issues. Please do write the
test, we should do this a lot more often.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2011-12-27 15:06 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-14 9:20 [PATCH 0/4] KVM: Dirty logging optimization using rmap Takuya Yoshikawa
2011-11-14 9:21 ` [PATCH 1/4] KVM: MMU: Clean up BUG_ON() conditions in rmap_write_protect() Takuya Yoshikawa
2011-11-14 9:22 ` [PATCH 2/4] KVM: MMU: Split gfn_to_rmap() into two functions Takuya Yoshikawa
2011-11-14 9:23 ` [PATCH 3/4] KVM: Count the number of dirty pages for dirty logging Takuya Yoshikawa
2011-11-14 10:07 ` Avi Kivity
2011-11-14 10:24 ` Avi Kivity
2011-12-20 4:29 ` Takuya Yoshikawa
2011-12-23 11:14 ` Marcelo Tosatti
2011-12-24 2:52 ` Takuya Yoshikawa
2011-12-27 13:50 ` Marcelo Tosatti
2011-12-27 14:03 ` Avi Kivity
2011-12-27 15:03 ` Takuya Yoshikawa
2011-12-27 15:06 ` Avi Kivity [this message]
2011-12-27 15:15 ` Takuya Yoshikawa
2011-12-27 15:18 ` Avi Kivity
2011-11-14 9:24 ` [PATCH 4/4] KVM: Optimize dirty logging by rmap_write_protect() Takuya Yoshikawa
2011-11-14 10:22 ` Avi Kivity
2011-11-14 10:29 ` Takuya Yoshikawa
2011-11-14 10:25 ` [PATCH 0/4] KVM: Dirty logging optimization using rmap Avi Kivity
2011-11-14 10:56 ` Takuya Yoshikawa
2011-11-14 12:39 ` Avi Kivity
2011-11-16 4:28 ` Takuya Yoshikawa
2011-11-16 9:06 ` Avi Kivity
2011-11-29 10:01 ` Xiao Guangrong
2011-11-29 10:09 ` Xiao Guangrong
2011-11-29 10:35 ` Takuya Yoshikawa
2011-11-29 11:20 ` Avi Kivity
2011-11-29 11:56 ` Xiao Guangrong
2011-11-29 12:01 ` Avi Kivity
2011-11-29 14:03 ` Avi Kivity
2011-11-30 5:02 ` Takuya Yoshikawa
2011-11-30 5:02 ` [Qemu-devel] " Takuya Yoshikawa
2011-11-30 5:15 ` Takuya Yoshikawa
2011-11-30 5:15 ` [Qemu-devel] " Takuya Yoshikawa
2011-12-01 15:18 ` Avi Kivity
2011-12-01 15:18 ` [Qemu-devel] " Avi Kivity
2011-12-03 4:37 ` Takuya Yoshikawa
2011-12-03 4:37 ` [Qemu-devel] " Takuya Yoshikawa
2011-12-04 10:20 ` Avi Kivity
2011-12-04 10:20 ` [Qemu-devel] " Avi Kivity
2011-11-30 7:10 ` Xiao Guangrong
2011-11-30 7:03 ` Xiao Guangrong
2011-12-01 15:11 ` Avi Kivity
2011-11-16 8:17 ` Takuya Yoshikawa
2011-11-16 8:17 ` [Qemu-devel] " Takuya Yoshikawa
2011-11-17 9:28 ` Avi Kivity
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