linux-kernel - Re: [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO

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Message-ID: <CAJSP0QW5wPYcHr02oNm8Y8=hsChEb5tJuO0ntPy9MO8EPuH=Qg@mail.gmail.com>
Date:	Thu, 22 Dec 2011 12:57:40 +0000
From:	Stefan Hajnoczi <stefanha@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Chris Wright <chrisw@...s-sol.org>,
	Jens Axboe <axboe@...nel.dk>,
	Stefan Hajnoczi <stefanha@...ux.vnet.ibm.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO

On Wed, Dec 21, 2011 at 1:00 AM, Minchan Kim <minchan@...nel.org> wrote:
> This patch is follow-up of Christohp Hellwig's work
> [RFC: ->make_request support for virtio-blk].
> http://thread.gmane.org/gmane.linux.kernel/1199763
>
> Quote from hch
> "This patchset allows the virtio-blk driver to support much higher IOP
> rates which can be driven out of modern PCI-e flash devices.  At this
> point it really is just a RFC due to various issues."

Basic question to make sure I understood this series: does this patch
bypass the guest I/O scheduler (but then you added custom batching
code into virtio_blk.c)?

If you're stumped by the performance perhaps compare blktraces of the
request approach vs the bio approach.  We're probably performing I/O
more CPU-efficiently but the I/O pattern itself is worse.

Stefan
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