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From: David Sterba <dsterba@suse.cz>
To: Chris Mason <clm@fb.com>
Cc: dsterba@suse.cz, Philip Worrall <philip.worrall@googlemail.com>,
	linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 0/8] Add support for LZ4 compression
Date: Thu, 12 Jun 2014 10:47:50 +0200
Message-ID: <20140612084750.GJ1903@twin.jikos.cz> (raw)
In-Reply-To: <538F2666.6030402@fb.com>

On Wed, Jun 04, 2014 at 10:00:06AM -0400, Chris Mason wrote:
> I have a slightly different reason for holding off on these.  Disk
> format changes are forever, and we need a really strong use case for
> pulling them in.

The format upgrade is inevitable for full bidirectional interoperability
of filesystems with non-pagesized sectorsize and compression. At the
moment this is not possible even without compression, but patches are on
the way.

> With that said, thanks for spending all of the time on this.  Pulling in
> Dave's idea to stream larger compression blocks through lzo (or any new
> alg) might be enough to push performance much higher, and better show
> case the differences between new algorithms.

The space savings and speed gains can be measured outside of btrfs.
>From the past numbers I see that 4k->64k chunk brings another 5-10% of
ratio and the de/compression speed is not worse.

Bigger chunks do not improve that much, but the overhead for assembling
the linear mappings would be decreased.

> The whole reason I chose zlib originally was because its streaming
> interface was a better fit for how FS IO worked.

Right, zlib has the streaming interface and accepts randomly scattered
blocks, but the others do not. LZ4 has a streaming extension proposed,
but I haven't looked at it closely whether it satisfies our constraints.

      reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-31 23:48 Philip Worrall
2014-05-31 23:48 ` [PATCH 1/8] Btrfs: Add kernel config options for LZ4 Philip Worrall
2014-05-31 23:48 ` [PATCH 2/8] Btrfs: Add lz4.c to the Makefile Philip Worrall
2014-05-31 23:48 ` [PATCH 3/8] Btrfs: Add lz4 compression to avaialble compression ops Philip Worrall
2014-05-31 23:48 ` [PATCH 4/8] Btrfs: Add definition for external lz4 compression struct Philip Worrall
2014-05-31 23:48 ` [PATCH 5/8] Btrfs: Add feature flags for LZ4 support Philip Worrall
2014-05-31 23:48 ` [PATCH 6/8] Btrfs: Ensure LZ4 feature flags are set when mounting with LZ4 Philip Worrall
2014-05-31 23:48 ` [PATCH 7/8] Btrfs: Add lz4 compression/decompression struct ops Philip Worrall
2014-05-31 23:48 ` [PATCH 8/8] Btrfs: Check for compress=lz4 in mount options Philip Worrall
2014-06-02 22:04 ` [PATCH 0/8] Add support for LZ4 compression Mitch Harder
2014-06-03 15:53 ` David Sterba
2014-06-04 14:00   ` Chris Mason
2014-06-12  8:47     ` David Sterba [this message]

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