linux-ext4 - Re: [PATCH 03/35] libext2fs/e2fsck: provide routines to read-ahead metadata

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Message-ID: <20150421030340.GD3238@thunk.org>
Date:	Mon, 20 Apr 2015 23:03:40 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 03/35] libext2fs/e2fsck: provide routines to read-ahead
 metadata

On Wed, Apr 01, 2015 at 07:34:19PM -0700, Darrick J. Wong wrote:
> This patch adds to e2fsck the ability to pre-fetch metadata into the
> page cache in the hopes of speeding up fsck runs.  There are two new
> functions -- the first allows a caller to readahead a list of blocks,
> and the second is a helper function that uses that first mechanism to
> load group data (bitmaps, inode tables).
> 
> These new e2fsck routines require the addition of a dblist API to
> allow us to iterate a subset of a dblist.  This will enable
> incremental directory block readahead in e2fsck pass 2.
> 
> There's also a function to estimate the readahead given a FS.
> 
> v2: Add an API to create a dblist with a given number of list elements
> pre-allocated.  This enables us to save ~2ms per call to
> e2fsck_readahead() (assuming a 2MB RA buffer) by not having to
> repeatedly call ext2_resize_mem as we add blocks to the list.
> 
> v3: Instead of creating dblists of arbitrary size, change the dblist
> iterator to allow iterating a sub-range.  This eliminates a lot of
> unnecessary list copying during e2fsck part2.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>

Thanks, applied.

						- Ted
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