From: Avi Kivity <avi@redhat.com>
To: Takuya Yoshikawa <takuya.yoshikawa@gmail.com>
Cc: yoshikawa.takuya@oss.ntt.co.jp, mtosatti@redhat.com,
qemu-devel <qemu-devel@nongnu.org>,
kvm@vger.kernel.org
Subject: Re: [Qemu-devel] Heavy memory_region_get_dirty() -- Re: [PATCH 0/1 v2] KVM: Alleviate mmu_lock contention during dirty logging
Date: Wed, 02 May 2012 14:33:55 +0300 [thread overview]
Message-ID: <4FA11BA3.2000605@redhat.com> (raw)
In-Reply-To: <20120502202414.37d760fbb1135bb8acb0f0db@gmail.com>
On 05/02/2012 02:24 PM, Takuya Yoshikawa wrote:
> During checking mmu_lock contention, I noticed that QEMU's
> memory_region_get_dirty() was using unexpectedly much CPU time.
>
> Thanks,
> Takuya
>
> =============================
> perf top -t ${QEMU_TID}
> =============================
> 51.52% qemu-system-x86_64 [.] memory_region_get_dirty
> 16.73% qemu-system-x86_64 [.] ram_save_remaining
>
memory_region_get_dirty() is called from ram_save_remaining(). Looks
like quadratic behaviour here: we send a few pages in
ram_save_remaining(), then walk the entire dirty bitmap to calculate
expected_time().
We should probably calculate expected_time once per iteration.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2012-05-02 11:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120428190544.7dc2bfd281054c1fcac5a14e@gmail.com>
2012-05-02 11:24 ` [Qemu-devel] Heavy memory_region_get_dirty() -- Re: [PATCH 0/1 v2] KVM: Alleviate mmu_lock contention during dirty logging Takuya Yoshikawa
2012-05-02 11:33 ` Avi Kivity [this message]
2012-05-02 14:20 ` Takuya Yoshikawa
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