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Re: [Qemu-devel] [Qemu-block] [PATCH v2 4/6] rbd: Switch to byte-based c
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [Qemu-block] [PATCH v2 4/6] rbd: Switch to byte-based callbacks |
Date: |
Wed, 25 Apr 2018 12:58:24 +0200 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
Am 24.04.2018 um 21:53 hat Jason Dillaman geschrieben:
> On Tue, Apr 24, 2018 at 3:25 PM, Eric Blake <address@hidden> wrote:
> > We are gradually moving away from sector-based interfaces, towards
> > byte-based. Make the change for the last few sector-based callbacks
> > in the rbd driver.
> >
> > Note that the driver was already using byte-based calls for
> > performing actual I/O, so this just gets rid of a round trip
> > of scaling; however, as I don't know if RBD is tolerant of
> > non-sector AIO operations, I went with the conservate approach
> > of adding .bdrv_refresh_limits to override the block layer
> > defaults back to the pre-patch value of 512.
> >
> > Signed-off-by: Eric Blake <address@hidden>
> >
> > ---
> > v2: override new block layer default alignment [Kevin]
> > ---
> > block/rbd.c | 44 ++++++++++++++++++++++++--------------------
> > 1 file changed, 24 insertions(+), 20 deletions(-)
> >
> > diff --git a/block/rbd.c b/block/rbd.c
> > index c9359d0ad84..638ecf8d986 100644
> > --- a/block/rbd.c
> > +++ b/block/rbd.c
> > @@ -231,6 +231,13 @@ done:
> > }
> >
> >
> > +static void qemu_rbd_refresh_limits(BlockDriverState *bs, Error **errp)
> > +{
> > + /* XXX Does RBD support AIO on less than 512-byte alignment? */
>
> Yes, librbd internally supports 1-byte alignment for IO, but the
> optimal alignment/length would be object size * stripe count.
Would you like to post a follow-up patch to this series that removes the
.bdrv_refresh_limits implementation again with a commit message
explaining that RBD does support byte alignment?
Kevin
- [Qemu-devel] [PATCH v2 0/6] block: byte-based AIO read/write, Eric Blake, 2018/04/24
- [Qemu-devel] [PATCH v2 5/6] vxhs: Switch to byte-based callbacks, Eric Blake, 2018/04/24
- [Qemu-devel] [PATCH v2 4/6] rbd: Switch to byte-based callbacks, Eric Blake, 2018/04/24
- [Qemu-devel] [PATCH v2 3/6] null: Switch to byte-based read/write, Eric Blake, 2018/04/24
- [Qemu-devel] [PATCH v2 1/6] block: Support byte-based aio callbacks, Eric Blake, 2018/04/24
- [Qemu-devel] [PATCH v2 2/6] file-win32: Switch to byte-based callbacks, Eric Blake, 2018/04/24
- [Qemu-devel] [PATCH v2 6/6] block: Drop last of the sector-based aio callbacks, Eric Blake, 2018/04/24
- Re: [Qemu-devel] [PATCH v2 0/6] block: byte-based AIO read/write, Kevin Wolf, 2018/04/25