On Fri, 25 Mar 2011 16:25:57 -0400 Jeff Layton <[email protected]> wrote:
> Commit 522440ed made cifs set backing_dev_info on the mapping attached > to new inodes. This change caused a fairly significant read performance > regression, as cifs started doing page-sized reads exclusively. > > By virtue of the fact that they're allocated as part of cifs_sb_info by > kzalloc, the ra_pages on cifs BDIs get set to 0, which prevents any > readahead. This forces the normal read codepaths to use readpage instead > of readpages causing a four-fold increase in the number of read calls > with the default rsize. > > Fix it by setting ra_pages in the BDI to the same value as that in the > default_backing_dev_info. > > Cc: [email protected] > Reported-and-Tested-by: Till <[email protected]> > Signed-off-by: Jeff Layton <[email protected]> > --- > fs/cifs/cifsfs.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c > index 1af2470..fb6a2ad 100644 > --- a/fs/cifs/cifsfs.c > +++ b/fs/cifs/cifsfs.c > @@ -131,6 +131,7 @@ cifs_read_super(struct super_block *sb, void *data, > kfree(cifs_sb); > return rc; > } > + cifs_sb->bdi.ra_pages = default_backing_dev_info.ra_pages; > > #ifdef CONFIG_CIFS_DFS_UPCALL > /* copy mount params to sb for use in submounts */ Forgot to mention that this fixes the following kernel.org bug: https://bugzilla.kernel.org/show_bug.cgi?id=31662 ...look there if you're curious about the gory details... -- Jeff Layton <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
