[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH 3/6] null: Switch to byte-based read/write
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH 3/6] null: Switch to byte-based read/write |
Date: |
Tue, 24 Apr 2018 17:52:05 +0200 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
Am 15.02.2018 um 20:28 hat Eric Blake geschrieben:
> We are gradually moving away from sector-based interfaces, towards
> byte-based. Make the change for the last few sector-based callbacks
> in the null-co and null-aio drivers.
>
> Note that since the null driver does nothing on writes, it trivially
> supports the BDRV_REQ_FUA flag (all writes have already landed to
> the same bit-bucket without needing an extra flush call). Furthermore,
> bdrv_refresh_limits() defaults the block size to 512 for any driver
> that does not support coroutines; while this is still correct for the
> other aio-based drivers, the null driver does just as well with
> byte-based requests, and being explicit means we can avoid cycles
> wasted on read-modify-write.
>
> Signed-off-by: Eric Blake <address@hidden>
> +static void null_refresh_limits(BlockDriverState *bs, Error **errp)
> +{
> + bs->bl.request_alignment = 1;
> +}
I would rather modify bdrv_refresh_limits() so that it defaults to 1 for
drivers supporting either .bdrv_co_preadv or .bdrv_aio_preadv.
Kevin
- Re: [Qemu-devel] [PATCH 3/6] null: Switch to byte-based read/write,
Kevin Wolf <=