From: Paolo Bonzini <pbonzini@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Stefan Hajnoczi <stefanha@gmail.com>,
Minchan Kim <minchan@kernel.org>,
Rusty Russell <rusty@rustcorp.com.au>,
Chris Wright <chrisw@sous-sol.org>, Jens Axboe <axboe@kernel.dk>,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO
Date: Mon, 02 Jan 2012 17:18:13 +0100 [thread overview]
Message-ID: <4F01D8C5.1060300@redhat.com> (raw)
In-Reply-To: <20120102161518.GA28940@infradead.org>
On 01/02/2012 05:15 PM, Christoph Hellwig wrote:
> > When QEMU uses O_DIRECT, the guest should not use QUEUE_FLAG_NONROT
> > unless it is active for the host disk as well. (In doubt, as is the
> > case for remote hosts accessed over NFS, I would also avoid NONROT
> > and allow more coalescing).
>
> Do we have any benchmark numbers where QUEUE_FLAG_NONROT makes a
> difference?
Not that I know of.
> I tried a few times, and the only constant measureable
> thing was that it regressed performance when used for rotating devices
> in a few benchmarks.
Were you trying with cache=none or writeback? For cache=none, that's
exactly what I'd expect. cache=writeback could be more interesting...
Paolo
next prev parent reply other threads:[~2012-01-02 16:18 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-21 1:00 [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO Minchan Kim
2011-12-21 1:00 ` [PATCH 1/6] block: add bio_map_sg Minchan Kim
2011-12-21 1:00 ` [PATCH 2/6] virtio: support unlocked queue kick Minchan Kim
2011-12-21 1:00 ` [PATCH 3/6] virtio-blk: remove the unused list of pending requests Minchan Kim
2011-12-21 1:00 ` [PATCH 4/6] virtio-blk: implement ->make_request Minchan Kim
2011-12-22 12:20 ` Stefan Hajnoczi
2011-12-22 20:28 ` Christoph Hellwig
2011-12-21 1:00 ` [PATCH 5/6] virtio-blk: Support batch I/O for enhancing sequential IO Minchan Kim
2011-12-21 1:00 ` [PATCH 6/6] virtio-blk: Emulate Flush/FUA Minchan Kim
2011-12-21 5:08 ` [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO Rusty Russell
2011-12-21 5:56 ` Minchan Kim
2011-12-21 8:28 ` Sasha Levin
2011-12-21 8:17 ` Minchan Kim
2011-12-21 19:11 ` Vivek Goyal
2011-12-22 1:05 ` Minchan Kim
2011-12-22 15:45 ` Vivek Goyal
2011-12-22 23:26 ` Minchan Kim
2011-12-22 12:57 ` Stefan Hajnoczi
2011-12-22 23:41 ` Minchan Kim
2012-01-01 16:45 ` Stefan Hajnoczi
2012-01-02 7:48 ` Dor Laor
2012-01-02 16:12 ` Paolo Bonzini
2012-01-02 16:15 ` Christoph Hellwig
2012-01-02 16:18 ` Paolo Bonzini [this message]
2012-01-02 16:23 ` Christoph Hellwig
2012-01-02 16:18 ` Christoph Hellwig
2012-01-02 16:21 ` Avi Kivity
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