From: Fam Zheng <famz@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
qemu-devel@nongnu.org, Alberto Garcia <berto@igalia.com>,
qemu-block@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] aio-posix: honor is_external in AioContext polling
Date: Tue, 24 Jan 2017 20:47:19 +0800 [thread overview]
Message-ID: <20170124124719.GG27126@lemon.Home> (raw)
In-Reply-To: <1c28bff5-4a36-5343-801c-dd4f891cf307@redhat.com>
On Tue, 01/24 13:15, Paolo Bonzini wrote:
>
>
> On 24/01/2017 13:04, Fam Zheng wrote:
> >
> > All in all I think we should skip external handlers regardless of
> > aio_disable_external(), or even skip try_poll_mode, in nested aio_poll()'s. The
> > reasons are 1) many nested aio_poll()'s don't have bdrv_drained_begin, so this
> > check is not sufficient [...] bdrv_flush()
> > spin longer than necessary, if not forever, when the guest keeps submitting more
> > requests with ioeventfd.
>
>
> I'm not sure I understand why this is related. aio_poll() only tries
> poll mode once, so bdrv_flush would only spin until the fsync is complete.
Right, I was confused. The problematic ones are "drain" style ones that tracks
a inflight counter. The only suspecious one is in v9fs_reset(), otherwise we are
safe!
Fam
next prev parent reply other threads:[~2017-01-24 12:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-24 9:53 [Qemu-devel] [PATCH] aio-posix: honor is_external in AioContext polling Stefan Hajnoczi
2017-01-24 12:04 ` Fam Zheng
2017-01-24 12:15 ` Paolo Bonzini
2017-01-24 12:47 ` Fam Zheng [this message]
2017-01-24 12:51 ` Paolo Bonzini
2017-01-24 13:40 ` Fam Zheng
2017-01-24 14:31 ` Alberto Garcia
2017-01-25 13:16 ` Stefan Hajnoczi
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