From: "Michael S. Tsirkin" <mst@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>, Ming Lei <tom.leiming@gmail.com>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH] virtio_blk: merge S/G list entries by default
Date: Mon, 8 Sep 2014 11:18:30 +0300 [thread overview]
Message-ID: <20140908081830.GA32268@redhat.com> (raw)
In-Reply-To: <20140907184745.GA23026@lst.de>
On Sun, Sep 07, 2014 at 08:47:45PM +0200, Christoph Hellwig wrote:
> 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.
Could you respond to Ming Lei's mail, who benchmarked the patch, please?
--
MST
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
Jens Axboe <axboe@kernel.dk>,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
Ming Lei <tom.leiming@gmail.com>
Subject: Re: [PATCH] virtio_blk: merge S/G list entries by default
Date: Mon, 8 Sep 2014 11:18:30 +0300 [thread overview]
Message-ID: <20140908081830.GA32268@redhat.com> (raw)
In-Reply-To: <20140907184745.GA23026@lst.de>
On Sun, Sep 07, 2014 at 08:47:45PM +0200, Christoph Hellwig wrote:
> 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.
Could you respond to Ming Lei's mail, who benchmarked the patch, please?
--
MST
next prev parent reply other threads:[~2014-09-08 8:18 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
2014-09-07 18:47 ` Christoph Hellwig
2014-09-08 8:18 ` Michael S. Tsirkin [this message]
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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