[lkml]   [2011]   [Dec]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO
On Thu, Dec 22, 2011 at 12:57:40PM +0000, Stefan Hajnoczi wrote:
> On Wed, Dec 21, 2011 at 1:00 AM, Minchan Kim <> wrote:
> > This patch is follow-up of Christohp Hellwig's work
> > [RFC: ->make_request support for virtio-blk].
> >
> >
> > 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.

You mean I/O scheduler have many techniques to do well in I/O pattern?
That's what I want to discuss in this RFC.

I guess request layer have many techniques proved during long time
to do well I/O but BIO-based drvier ignores them for just reducing locking
overhead. Of course, we can add such techniques to BIO-batch driver like
custom-batch in this series. But it needs lots of work, is really duplication,
and will have a problem on maintenance.

I would like to listen opinions whether this direction is good or bad.

> Stefan

Kind regards,
Minchan Kim
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2011-12-23 00:45    [W:0.126 / U:11.136 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site