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From: Andi Kleen <andi@firstfloor.org>
To: Olaf Weber <olaf@sgi.com>
Cc: linux-fsdevel@vger.kernel.org, Ben Myers <bpm@sgi.com>,
	Andi Kleen <andi@firstfloor.org>,
	tinguely@sgi.com, xfs@oss.sgi.com
Subject: Re: [RFC v2] Unicode/UTF-8 support for XFS
Date: Tue, 23 Sep 2014 22:15:40 +0200	[thread overview]
Message-ID: <20140923201540.GB15923@two.firstfloor.org> (raw)
In-Reply-To: <54219C17.3090104@sgi.com>

> You only pay the space cost if you use it, similar to the nls tables.

The way Linux module loading works these things are loaded by default,
not when someone needs it.

So no, you (or rather every unfortunate Linux XFS user) would pay it always,
unless you black list the module or rebuild the kernel.

> A big part of the table does decompositions for Korean: eliminating
> the Hangul decompositions removes 156320 bytes, leaving 89936 bytes.

Are there regular ranges or other redundancies in the Korean encoding
that could be used to compress paths?

Doing some basic research other people already answered this:

Please use the ICU or google tables referenced below. Apparently
smaller is possible too, but 40-50k seems more reasonable.

I'm just gonna make the claim that whatever performance you
get from a larger table is dwarfed by the cache miss overhead.

----

http://macchiato.com/unicode/normalization_footprint.htm

http://www.macchiato.com/unicode/nfc-faq

NFC normalization requires large tables, right?
Like many other cases, there is a tradeoff between size and performance.
You can use very small tables, at some cost in performance. (Even there,
the actual performance cost depends on how often normalization needs to
be invoked, as discussed above.)

To see an analysis of the situation, see Normalization Footprint. It is
a bit out of date, but gives a sense of the magnitude. For comparison,
ICU's optimized tables for NFC take 44 kB (UTF-16) and Google's
optimized tables for NFC take 46 kB (UTF-8).


-Andi

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  reply	other threads:[~2014-09-23 20:15 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-18 19:56 [RFC v2] Unicode/UTF-8 support for XFS Ben Myers
2014-09-18 20:08 ` [PATCH 01/10] xfs: return the first match during case-insensitive lookup Ben Myers
2014-09-18 20:09 ` [PATCH 02/10] xfs: rename XFS_CMP_CASE to XFS_CMP_MATCH Ben Myers
2014-09-18 20:09 ` [PATCH 03/13] libxfs: add xfs_nameops.normhash Ben Myers
2014-09-18 20:10 ` [PATCH 04/10] xfs: change interface of xfs_nameops.normhash Ben Myers
2014-09-18 20:11 ` [PATCH 05/10] xfs: add a superblock feature bit to indicate UTF-8 support Ben Myers
2014-09-18 20:13 ` [PATCH 03/10] xfs: add xfs_nameops.normhash Ben Myers
2014-09-18 20:14 ` [PATCH 06/10] xfs: add unicode character database files Ben Myers
2014-09-22 20:54   ` Dave Chinner
2014-09-26 17:09     ` Christoph Hellwig
2014-09-18 20:15 ` [PATCH 07/10] xfs: add trie generator and supporting code for UTF-8 Ben Myers
2014-09-22 20:57   ` Dave Chinner
2014-09-23 18:57     ` Ben Myers
2014-09-26 17:10       ` Christoph Hellwig
2014-09-18 20:16 ` [PATCH 08/10] xfs: add xfs_nameops for utf8 and utf8+casefold Ben Myers
2014-09-18 20:17 ` [PATCH 09/10] xfs: apply utf-8 normalization rules to user extended attribute names Ben Myers
2014-09-18 20:18 ` [PATCH 10/10] xfs: implement demand load of utf8norm.ko Ben Myers
2014-09-18 20:31 ` [PATCH 00/13] xfsprogs: Unicode/UTF-8 support for XFS Ben Myers
2014-09-18 20:33   ` [PATCH 01/13] libxfs: return the first match during case-insensitive lookup Ben Myers
2014-09-18 20:33   ` [PATCH 02/13] libxfs: rename XFS_CMP_CASE to XFS_CMP_MATCH Ben Myers
2014-09-18 20:34   ` [PATCH 03/13] libxfs: add xfs_nameops.normhash Ben Myers
2014-09-18 20:35   ` [PATCH 04/13] libxfs: change interface of xfs_nameops.normhash Ben Myers
2014-09-18 20:36   ` [PATCH 05/13] libxfs: add a superblock feature bit to indicate UTF-8 support Ben Myers
2014-09-18 20:37   ` [PATCH 06/13] xfsprogs: add unicode character database files Ben Myers
2014-09-18 20:38   ` [PATCH 07/13] libxfs: add trie generator and supporting code for UTF-8 Ben Myers
2014-09-18 20:38   ` [PATCH 08/13] libxfs: add xfs_nameops for utf8 and utf8+casefold Ben Myers
2014-09-18 20:39   ` [PATCH 09/13] libxfs: apply utf-8 normalization rules to user extended attribute names Ben Myers
2014-09-18 20:40   ` [PATCH 10/13] xfsprogs: add utf8 support to growfs Ben Myers
2014-09-18 20:41   ` [PATCH 11/13] xfsprogs: add utf8 support to mkfs.xfs Ben Myers
2014-09-18 20:42   ` [PATCH 12/13] xfsprogs: add utf8 support to xfs_repair Ben Myers
2014-09-18 20:43   ` [PATCH 13/13] xfsprogs: add a preliminary test for utf8 support Ben Myers
2014-09-19 16:06   ` [PATCH 07a/13] xfsprogs: add trie generator for UTF-8 Ben Myers
2014-09-23 18:34     ` Roger Willcocks
2014-09-24 23:11       ` Ben Myers
2014-09-19 16:07   ` [PATCH 07b/13] libxfs: add supporting code " Ben Myers
2014-09-18 21:10 ` [RFC v2] Unicode/UTF-8 support for XFS Ben Myers
2014-09-18 21:24   ` Zach Brown
2014-09-18 22:23     ` Ben Myers
2014-09-19 16:03 ` [PATCH 07a/10] xfs: add trie generator for UTF-8 Ben Myers
2014-09-19 16:04 ` [PATCH 07b/10] xfs: add supporting code " Ben Myers
2014-09-22 14:55 ` [RFC v2] Unicode/UTF-8 support for XFS Andi Kleen
2014-09-22 18:41   ` Ben Myers
2014-09-22 19:29     ` Andi Kleen
2014-09-23 16:13       ` Olaf Weber
2014-09-23 20:15         ` Andi Kleen [this message]
2014-09-23 20:45           ` Ben Myers
2014-09-24 11:07           ` Olaf Weber
2014-09-26 14:06             ` Olaf Weber
2014-09-23 13:01   ` Olaf Weber
2014-09-23 20:02     ` Andi Kleen
2014-09-22 22:26 ` Dave Chinner
2014-09-24 13:21   ` Olaf Weber
2014-09-24 23:10     ` Dave Chinner
2014-09-25 13:33       ` Zuckerman, Boris
2014-09-26 14:50       ` Olaf Weber
2014-09-26 16:56         ` Christoph Hellwig
2014-09-26 17:04           ` Jeremy Allison
2014-09-26 17:06             ` Christoph Hellwig
2014-09-26 17:13               ` Jeremy Allison
2014-09-26 19:37             ` Olaf Weber
2014-09-26 19:46               ` Jeremy Allison
2014-09-26 20:03                 ` Olaf Weber
2014-09-29 20:16                   ` J. Bruce Fields
2014-09-29 11:06               ` Christoph Hellwig
2014-09-26 17:30           ` Ben Myers

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