From: Kevin Wolf <kwolf@redhat.com>
To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: Fam Zheng <famz@redhat.com>, Hu Tao <hutao@cn.fujitsu.com>,
qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Yasunori Goto <y-goto@jp.fujitsu.com>
Subject: Re: [Qemu-devel] [PATCH v13 5/6] raw-posix: Add full preallocation option
Date: Thu, 4 Sep 2014 14:52:57 +0200 [thread overview]
Message-ID: <20140904125257.GI3897@noname.str.redhat.com> (raw)
In-Reply-To: <20140904124519.GB1302@redhat.com>
Am 04.09.2014 um 14:45 hat Richard W.M. Jones geschrieben:
> On Thu, Sep 04, 2014 at 02:35:22PM +0200, Kevin Wolf wrote:
> > Please change the code to always write zeros for FULL,
>
> How is this useful for anyone? You don't know if the underlying SAN
> is going to detect these zeroes or combine these blocks together.
> It's just slow for no reason.
It's slow for the reason that the user has requested it. Do you doubt
that users can know what their backend is doing? Why are you insisting
on providing only the functionality that you personally need?
I doubt it's a way to make many users happier, but if you insist, we can
leave full preallocation unsupported on raw-posix and allow only
metadata preallocation (which should still be fallocate() without a
zero-write fallback, so that you can rely on it being fast). But call it
by its name and don't say "full" when you only implement "metadata".
Kevin
next prev parent reply other threads:[~2014-09-04 12:53 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-29 8:33 [Qemu-devel] [PATCH v13 0/6] qcow2, raw: add preallocation=full Hu Tao
2014-08-29 8:33 ` [Qemu-devel] [PATCH v13 1/6] block: round up file size to nearest sector Hu Tao
2014-08-29 12:50 ` Eric Blake
2014-09-04 9:33 ` Kevin Wolf
2014-09-02 21:21 ` Max Reitz
2014-09-04 9:43 ` Kevin Wolf
2014-08-29 8:33 ` [Qemu-devel] [PATCH v13 2/6] block: don't convert file size to sector size Hu Tao
2014-09-02 21:24 ` Max Reitz
2014-09-04 9:57 ` Kevin Wolf
2014-09-05 9:07 ` Hu Tao
2014-08-29 8:33 ` [Qemu-devel] [PATCH v13 3/6] rename parse_enum_option to qapi_enum_parse and make it public Hu Tao
2014-09-02 21:27 ` Max Reitz
2014-09-03 1:30 ` Hu Tao
2014-09-04 10:03 ` Kevin Wolf
2014-08-29 8:33 ` [Qemu-devel] [PATCH v13 4/6] qapi: introduce PreallocMode and a new PreallocMode full Hu Tao
2014-09-02 21:32 ` Max Reitz
2014-09-03 1:31 ` Hu Tao
2014-09-02 21:51 ` Eric Blake
2014-09-03 1:35 ` Hu Tao
2014-09-04 12:17 ` Kevin Wolf
2014-08-29 8:33 ` [Qemu-devel] [PATCH v13 5/6] raw-posix: Add full preallocation option Hu Tao
2014-08-29 8:48 ` Richard W.M. Jones
2014-09-03 1:26 ` Hu Tao
2014-09-04 8:32 ` Hu Tao
2014-09-02 21:45 ` Max Reitz
2014-09-03 1:55 ` Hu Tao
2014-09-04 12:35 ` Kevin Wolf
2014-09-04 12:45 ` Richard W.M. Jones
2014-09-04 12:52 ` Kevin Wolf [this message]
2014-09-04 13:07 ` Richard W.M. Jones
2014-09-04 13:13 ` Daniel P. Berrange
2014-09-04 13:17 ` Kevin Wolf
2014-09-04 13:43 ` Richard W.M. Jones
2014-09-04 15:23 ` Kevin Wolf
2014-09-04 15:33 ` Richard W.M. Jones
2014-08-29 8:33 ` [Qemu-devel] [PATCH v13 6/6] qcow2: " Hu Tao
2014-09-02 21:55 ` Max Reitz
2014-09-04 13:09 ` Kevin Wolf
2014-09-09 3:23 ` Hu Tao
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