From: Vivek Goyal <vgoyal@redhat.com>
To: Minchan Kim <minchan@kernel.org>
Cc: 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,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO
Date: Thu, 22 Dec 2011 10:45:06 -0500 [thread overview]
Message-ID: <20111222154506.GC1388@redhat.com> (raw)
In-Reply-To: <20111222010538.GA9879@barrios-laptop.redhat.com>
On Thu, Dec 22, 2011 at 10:05:38AM +0900, Minchan Kim wrote:
[..]
> > May be using deadline or noop in guest is better to benchmark against
> > PCI-E based flash.
>
> Good suggestion.
> I tested it by deadline on guest side.
>
> The result is not good.
> Although gap is within noise, Batch BIO's random performance is regressed
> compared to CFQ.
>
> Request Batch BIO
>
> (MB/s) stddev (MB/s) stddev
> w 787.030 31.494 w 748.714 68.490
> rw 216.044 29.734 rw 216.977 40.635
> r 771.765 3.327 r 771.107 4.299
> rr 280.096 25.135 rr 258.067 43.916
>
> I did some small test for only Batch BIO with deadline and cfq.
> to see I/O scheduler's effect.
> I think result is very strange, deadline :149MB, CFQ : 87M
> Because Batio BIO patch uses make_request_fn instead of request_rfn.
> So I think we should not affect by I/O scheduler.(I mean we issue I/O
> before I/O scheduler handles it)
>
> What do you think about it?
> Do I miss something?
This indeed is very strange. In case of bio based drivers, changing IO
scheduler on the queue should not change anything.
Trying running blktrace on the vda devie and see if you notice something
odd.
Also you seem to be reporting contracdicting results for batch bio.
Initially you mention that random IO is regressing with deadline as
comapred to CFQ. (It dropped from 325.976 MB/s to 258.067 MB/s).
In this second test you are reporting that CFQ performs badly as
compared to deadline. (149MB/s vs 87MB/s).
Two contradicting results?
Thanks
Vivek
next prev parent reply other threads:[~2011-12-22 15:45 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 [this message]
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
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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