From: Li Zefan <lizefan@huawei.com>
To: <dave@jikos.cz>
Cc: Ben Wreder <benwreder@hotmail.com>, <linux-btrfs@vger.kernel.org>
Subject: Re: Tail packing
Date: Mon, 3 Sep 2012 09:23:10 +0800 [thread overview]
Message-ID: <5044067E.7000607@huawei.com> (raw)
In-Reply-To: <20120902052537.GF17430@twin.jikos.cz>
On 2012/9/2 13:25, David Sterba wrote:
> On Fri, Aug 31, 2012 at 04:40:36PM +0200, Ben Wreder wrote:
>> The disk format description implies that btrfs should be able to
>> support tail packing. I just did some experimentation, and while small
>> files are packed, it seems that files occupying more than one block
>> are not. For example, a lot of 32769-byte files will end up taking
>> over 36KB on average (a small excess due to the metadata itself).
>>
>> So just to confirm - btrfs does not currently support tail-packing, is that correct?
>
> Currently it's not the reiserfs-style tail packing. The feature is
> advertised as "Space-efficient packing of small files", as Josef
> replied, if a file fits into a leaf block, it's stored into the metadata
> blocks. The limit is 3916 bytes for 4k blocks, without compression. If
> compression is on, the 'small file' size limit is even higher for
> moderately compressible files.
If the actual size of the file is > 3916 bytes, no matter how compressible it is,
it won't be inlined.
> An example where this could apply is a
> maildir, and IIRC this was why reiserfs was chosen on mail servers.
>
next prev parent reply other threads:[~2012-09-03 1:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-31 14:40 Tail packing Ben Wreder
2012-08-31 15:03 ` Josef Bacik
2012-09-02 5:25 ` David Sterba
2012-09-03 1:23 ` Li Zefan [this message]
2012-09-03 16:49 ` David Sterba
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