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Re: [Qemu-devel] [PATCH 0/6] block: do request processing in a coroutine
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH 0/6] block: do request processing in a coroutine |
Date: |
Wed, 12 Oct 2011 15:21:27 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110927 Thunderbird/7.0 |
Am 05.10.2011 18:17, schrieb Stefan Hajnoczi:
> Block layer features like dirty block tracing, I/O throttling, and live block
> copy are forced to duplicate code due to the three different interfaces:
> synchronous, asynchronous, and coroutines.
>
> Since there are bdrv_read(), bdrv_aio_readv(), and bdrv_co_readv() interfaces
> for read (and similar for write), per-request processing needs to be
> duplicated
> for each of these execution contexts. For example, dirty block tracking code
> is duplicated across these three interfaces.
>
> This patch series unifies request processing so that there is only one code
> path. I see this as a prerequisite to the live block copy (image streaming)
> code I am working on, so I'm pushing it now.
>
> The short-term win from this series is that it becomes easy to add live block
> copy and other features. We now have a single code path where the
> perf-request
> processing is done.
>
> The longer-term win will be dropping the BlockDriver .bdrv_read(),
> .bdrv_write(), .bdrv_aio_readv(), and .bdrv_aio_writev() interfaces. By doing
> that we can bring all BlockDrivers onto a common interface, namely
> .bdrv_co_readv() and .bdrv_co_writev(). It will also allow us to drop most of
> the sync and aio emulation code.
>
> A consequence of this patch series is that every I/O request goes through at
> least one coroutine. There is no longer a direct .bdrv_read(), .bdrv_write(),
> .bdrv_aio_readv(), or .bdrv_aio_writev() call - we're trying to phase out
> those
> interfaces. I have not noticed performance degradation in correctness tests
> but we need to confirm that there has not been a performance regression.
>
> Stefan Hajnoczi (6):
> block: directly invoke .bdrv_aio_*() in bdrv_co_io_em()
> block: split out bdrv_co_do_readv() and bdrv_co_do_writev()
> block: switch bdrv_read()/bdrv_write() to coroutines
> block: switch bdrv_aio_readv() to coroutines
> block: mark blocks dirty on coroutine write completion
> block: switch bdrv_aio_writev() to coroutines
>
> block.c | 273
> +++++++++++++++++++++++++++++++--------------------------------
> 1 files changed, 134 insertions(+), 139 deletions(-)
>
Except for breaking synchronous drivers this looks good.
I have applied the first two patches to the block branch, so if you
don't need to change them, submitting patches 3-6 for v2 will be enough.
Kevin
[Qemu-devel] [PATCH 2/6] block: split out bdrv_co_do_readv() and bdrv_co_do_writev(), Stefan Hajnoczi, 2011/10/05
[Qemu-devel] [PATCH 5/6] block: mark blocks dirty on coroutine write completion, Stefan Hajnoczi, 2011/10/05
[Qemu-devel] [PATCH 6/6] block: switch bdrv_aio_writev() to coroutines, Stefan Hajnoczi, 2011/10/05
[Qemu-devel] [PATCH 1/6] block: directly invoke .bdrv_aio_*() in bdrv_co_io_em(), Stefan Hajnoczi, 2011/10/05
Re: [Qemu-devel] [PATCH 0/6] block: do request processing in a coroutine, Zhi Yong Wu, 2011/10/11
Re: [Qemu-devel] [PATCH 0/6] block: do request processing in a coroutine,
Kevin Wolf <=