From: Kevin Wolf <kwolf@redhat.com>
To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH v4 2/6] block: add .bdrv_co_write_zeroes() interface
Date: Mon, 06 Feb 2012 17:00:27 +0100 [thread overview]
Message-ID: <4F2FF91B.5050203@redhat.com> (raw)
In-Reply-To: <CAJSP0QXSbtjoCk3JPp7SiY+vU577zAXwUuntmhQXB5mZmR6bxQ@mail.gmail.com>
Am 06.02.2012 16:50, schrieb Stefan Hajnoczi:
> On Tue, Jan 24, 2012 at 3:16 PM, Kevin Wolf <kwolf@redhat.com> wrote:
>>> +/*
>>> + * Efficiently zero a region of the disk image. Note that this is a regular
>>> + * I/O request like read or write and should have a reasonable size. This
>>> + * function is not suitable for zeroing the entire image in a single request.
>>> + */
>>
>> The reason for this is that in the fallback case you allocate memory for
>> the whole request, right? So what about just limiting the allocation in
>> bdrv_co_do_write_zeroes() to a reasonable size and putting a loop there
>> for large requests?
>
> I'd rather not do that yet. We don't have a reasonable way to cancel
> such a request yet. In the future, if we decide we'd like to do huge
> bdrv_co_write_zeroes(), we could look at the details of making this
> work.
Do we even need a way to cancel such requests?
But anyway, include the reason in the comment, then we can leave it as
it is.
Kevin
next prev parent reply other threads:[~2012-02-06 15:57 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-18 14:59 [Qemu-devel] [PATCH v4 0/6] block: zero writes Stefan Hajnoczi
2012-01-18 14:59 ` [Qemu-devel] [PATCH v4 1/6] cutils: extract buffer_is_zero() from qemu-img.c Stefan Hajnoczi
2012-01-24 15:03 ` Kevin Wolf
2012-02-06 15:37 ` Stefan Hajnoczi
2012-01-18 14:59 ` [Qemu-devel] [PATCH v4 2/6] block: add .bdrv_co_write_zeroes() interface Stefan Hajnoczi
2012-01-24 15:16 ` Kevin Wolf
2012-02-06 15:50 ` Stefan Hajnoczi
2012-02-06 16:00 ` Kevin Wolf [this message]
2012-02-06 16:16 ` Stefan Hajnoczi
2012-01-18 14:59 ` [Qemu-devel] [PATCH v4 3/6] block: perform zero-detection during copy-on-read Stefan Hajnoczi
2012-01-18 14:59 ` [Qemu-devel] [PATCH v4 4/6] qed: replace is_write with flags field Stefan Hajnoczi
2012-01-18 14:59 ` [Qemu-devel] [PATCH v4 5/6] qed: add .bdrv_co_write_zeroes() support Stefan Hajnoczi
2012-01-18 14:59 ` [Qemu-devel] [PATCH v4 6/6] qemu-io: add write -z option for bdrv_co_write_zeroes Stefan Hajnoczi
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