[lkml]   [2007]   [Jun]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [patch 00/14] Page cache cleanup in anticipation of Large Blocksize support
On Thu, 14 Jun 2007 19:04:27 -0700 (PDT) Christoph Lameter <> wrote:

> > > Of course there is. The seeks are reduced since there are an factor
> > > of 16 less metadata blocks. fsck does not read files. It just reads
> > > metadata structures. And the larger contiguous areas the faster.
> >
> > Some metadata is contiguous: inode tables, some directories (if they got
> > lucky), bitmap tables. But fsck surely reads them in a single swoop
> > anyway, so there's no gain there.
> The metadata needs to refer to 1/16th of the earlier pages that need to be
> tracked. metadata is shrunk significantly.

Only if the filesystems are altered to use larger blocksizes and if the
operator then chooses to use that feature. Then they suck for small-sized
(and even medium-sized) files.

So you're still talking about corner cases: specialised applications which
require careful setup and administrator intervention.

What can we do to optimise the common case?

> > Other metadata (indirect blocks) are 100% discontiguous, and reading those
> > with a 64k IO into 64k of memory is completely dumb.
> The effect of a larger page size is that the filesystem will
> place more meta data into a single page instead of spreading it out.
> Reading a mass of meta data with a 64k read is an intelligent choice to
> make in particular if there is a large series of such reads.

Again: requires larger blocksize: specialised, uninteresting for what will
remain the common case: 4k blocksize.

The alleged fsck benefit is also unrelated to variable PAGE_CACHE_SIZE.
It's a feature of larger (unweildy?) blocksize, and xfs already has that
working (doesn't it?)

There may be some benefits to some future version of ext4.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-06-15 04:27    [W:0.053 / U:0.252 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site