From: Christoph Hellwig <hch@lst.de>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
virtualization@lists.linux-foundation.org,
Christoph Hellwig <hch@lst.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] virtio_blk: merge S/G list entries by default
Date: Sun, 7 Sep 2014 20:47:45 +0200 [thread overview]
Message-ID: <20140907184745.GA23026@lst.de> (raw)
In-Reply-To: <20140907114153.GB26569@redhat.com>
On Sun, Sep 07, 2014 at 02:41:53PM +0300, Michael S. Tsirkin wrote:
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> OK so this is an optimization patch right?
> What kind of performance gain is observed with it?
None. I actually wrote it when the block layer had a bug when dm was
used on top of the !merge case, and I decided to send it out as there had been
no discussion about disabling this by default on the existing blk-mq
drivers.
At least for my qemu/kvm setup it doesn't make a difference either way,
although not doing the cheap merge doesn't like the right kind of optimization
to me.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
Rusty Russell <rusty@rustcorp.com.au>,
Jens Axboe <axboe@kernel.dk>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH] virtio_blk: merge S/G list entries by default
Date: Sun, 7 Sep 2014 20:47:45 +0200 [thread overview]
Message-ID: <20140907184745.GA23026@lst.de> (raw)
In-Reply-To: <20140907114153.GB26569@redhat.com>
On Sun, Sep 07, 2014 at 02:41:53PM +0300, Michael S. Tsirkin wrote:
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> OK so this is an optimization patch right?
> What kind of performance gain is observed with it?
None. I actually wrote it when the block layer had a bug when dm was
used on top of the !merge case, and I decided to send it out as there had been
no discussion about disabling this by default on the existing blk-mq
drivers.
At least for my qemu/kvm setup it doesn't make a difference either way,
although not doing the cheap merge doesn't like the right kind of optimization
to me.
next prev parent reply other threads:[~2014-09-07 18:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-06 23:09 [PATCH] virtio_blk: merge S/G list entries by default Christoph Hellwig
2014-09-07 10:18 ` Paolo Bonzini
2014-09-07 10:32 ` Ming Lei
2014-09-07 10:32 ` Ming Lei
2014-09-10 15:18 ` Paolo Bonzini
2014-09-10 15:18 ` Paolo Bonzini
2014-09-10 15:21 ` Ming Lei
2014-09-10 15:21 ` Ming Lei
2014-09-07 11:41 ` Michael S. Tsirkin
2014-09-07 11:41 ` Michael S. Tsirkin
2014-09-07 18:47 ` Christoph Hellwig [this message]
2014-09-07 18:47 ` Christoph Hellwig
2014-09-08 8:18 ` Michael S. Tsirkin
2014-09-08 8:18 ` Michael S. Tsirkin
2014-09-08 20:15 ` Christoph Hellwig
2014-09-08 20:15 ` Christoph Hellwig
2014-09-10 16:43 ` Michael S. Tsirkin
2014-09-10 16:43 ` Michael S. Tsirkin
2014-09-08 16:21 ` Paolo Bonzini
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