lkml.org 
[lkml]   [2008]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
DateThu, 21 Aug 2008 20:27:50 -0700
From"Jared Hulbert" <>
SubjectRe: [PATCH 04/10] AXFS: axfs_inode.c
> I assume compressed blocks can be larger than PAGE_CACHE_SIZE?  This suffers
> from the rather obvious inefficiency that you decompress a big block >
> PAGE_CACHE_SIZE, but only copy one PAGE_CACHE_SIZE page out of it. If
> multiple files are being read simultaneously (a common occurrence), then
> each is going to replace your one cached uncompressed block
> (sbi->current_cnode_index), leading to decompressing the same blocks over
> and over again on sequential file access.
>
> readpage file A, index 1 -> decompress block X
> readpage file B, index 1 -> decompress block Y (replaces X)
> readpage file A, index 2 -> repeated decompress of block X (replaces Y)
> readpage file B, index 2 -> repeated decompress of block Y (replaces X)
>
> and so on.

Yep. Been thinking about optimizing it. So far it hasn't been an
issue for my customers. Most fs traffic being on the XIP pages. Once
I get a good automated performance test up we'll probably look into
something to improve this.


\
 
 \ /
  Last update: 2008-08-22 05:31    [from the cache]
©2003-2010