From: Paolo Bonzini <pbonzini@redhat.com>
To: Fam Zheng <famz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org,
Stefan Hajnoczi <stefanha@redhat.com>,
jsnow@redhat.com, wangxiaolong@ucloud.cn
Subject: Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard
Date: Mon, 11 May 2015 10:33:38 +0200 [thread overview]
Message-ID: <55506962.5050506@redhat.com> (raw)
In-Reply-To: <20150511080226.GB11990@fam-t430.nay.redhat.com>
On 11/05/2015 10:02, Fam Zheng wrote:
>
> /*
> * ...
> *
> * 'pnum' is set to the number of sectors (including and immediately following
> * the specified sector) that are known to be in the same
> * allocated/unallocated state.
> *
> * 'nb_sectors' is the max value 'pnum' should be set to. If nb_sectors goes
> * beyond the end of the disk image it will be clamped.
> */
> static int64_t coroutine_fn bdrv_co_get_block_status(BlockDriverState *bs,
>
> So we currently don't coalesce the sequential dirty sectors.
>
> Was that intentional?
The idea, I think, is that for some drivers bdrv_co_get_block_status is
O(nb_sectors).
It's okay to let a driver return *pnum > nb_sectors. You do need to
audit the callers, though. It would be nice also to add TODOs whenever
the code is fine but it could explot *pnum > nb_sectors to get better
performance.
Paolo
next prev parent reply other threads:[~2015-05-11 8:33 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-05 12:46 [Qemu-devel] [PATCH 0/4] block: Mirror discarded sectors Fam Zheng
2015-05-05 12:46 ` [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard Fam Zheng
2015-05-05 13:06 ` Paolo Bonzini
2015-05-06 1:45 ` Fam Zheng
2015-05-06 8:59 ` Paolo Bonzini
2015-05-06 9:50 ` Fam Zheng
2015-05-06 10:21 ` Paolo Bonzini
2015-05-11 8:02 ` Fam Zheng
2015-05-11 8:33 ` Paolo Bonzini [this message]
2015-05-05 12:46 ` [Qemu-devel] [PATCH 2/4] block: Remove bdrv_reset_dirty Fam Zheng
2015-05-05 21:57 ` Eric Blake
2015-05-05 12:46 ` [Qemu-devel] [PATCH 3/4] qemu-iotests: Make block job methods common Fam Zheng
2015-05-05 22:17 ` John Snow
2015-05-06 1:48 ` Fam Zheng
2015-05-05 12:46 ` [Qemu-devel] [PATCH 4/4] qemu-iotests: Add test case for mirror with unmap Fam Zheng
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