From: Josef Bacik <jbacik@fusionio.com>
To: Miao Xie <miaox@cn.fujitsu.com>
Cc: <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH] Btrfs: allocate the free space by the existed max extent size when ENOSPC
Date: Thu, 29 Aug 2013 15:34:59 -0400 [thread overview]
Message-ID: <20130829193459.GD10591@localhost.localdomain> (raw)
In-Reply-To: <1377755258-2722-1-git-send-email-miaox@cn.fujitsu.com>
On Thu, Aug 29, 2013 at 01:47:38PM +0800, Miao Xie wrote:
> By the current code, if the requested size is very large, and all the extents
> in the free space cache are small, we will waste lots of the cpu time to cut
> the requested size in half and search the cache again and again until it gets
> down to the size the allocator can return. In fact, we can know the max extent
> size in the cache after the first search, so we needn't cut the size in half
> repeatedly, and just use the max extent size directly. This way can save
> lots of cpu time and make the performance grow up when there are only fragments
> in the free space cache.
>
> According to my test, if there are only 4KB free space extents in the fs,
> and the total size of those extents are 256MB, we can reduce the execute
> time of the following test from 5.4s to 1.4s.
> dd if=/dev/zero of=<testfile> bs=1MB count=1 oflag=sync
>
> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
This breaks one of the free space cache unit tests, please enable the sanity
tests when you mess with free-space-cache.c so you can be sure you aren't
breaking anything. Thanks,
Josef
next prev parent reply other threads:[~2013-08-29 19:35 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-29 5:47 [PATCH] Btrfs: allocate the free space by the existed max extent size when ENOSPC Miao Xie
2013-08-29 12:45 ` David Sterba
2013-08-30 10:58 ` Miao Xie
2013-08-29 19:34 ` Josef Bacik [this message]
-- strict thread matches above, loose matches on Subject: below --
2013-08-30 10:35 Miao Xie
2013-09-06 13:47 ` Stefan Behrens
2013-09-09 6:21 ` Miao Xie
2013-09-09 9:06 ` Stefan Behrens
2013-09-17 13:13 ` David Sterba
2013-09-18 4:04 ` Miao Xie
2013-09-20 9:25 ` David Sterba
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