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cifs: don't cap ra_pages at the same level as default_backing_dev_info

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While testing, I've found that even when we are able to negotiate a
much larger rsize with the server, on-the-wire reads often end up being
capped at 128k because of ra_pages being capped at that level.

Lifting this restriction gave almost a twofold increase in sequential
read performance on my craptactular KVM test rig with a 1M rsize.

I think this is safe since the actual ra_pages that the VM requests
is run through max_sane_readahead() prior to submitting the I/O. Under
memory pressure we should end up with large readahead requests being
suppressed anyway.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
This commit is contained in:
Jeff Layton 2012-05-01 17:41:49 -04:00 committed by Steve French
parent 156d17905e
commit 8f71465c19
1 changed files with 1 additions and 17 deletions
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18
fs/cifs/connect.c
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@ -3614,22 +3614,6 @@ cifs_get_volume_info(char *mount_data, const char *devname)
return volume_info;
}
/* make sure ra_pages is a multiple of rsize */
static inline unsigned int
cifs_ra_pages(struct cifs_sb_info *cifs_sb)
{
unsigned int reads;
unsigned int rsize_pages = cifs_sb->rsize / PAGE_CACHE_SIZE;
if (rsize_pages >= default_backing_dev_info.ra_pages)
return default_backing_dev_info.ra_pages;
else if (rsize_pages == 0)
return rsize_pages;
reads = default_backing_dev_info.ra_pages / rsize_pages;
return reads * rsize_pages;
}
int
cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info)
{
@ -3717,7 +3701,7 @@ try_mount_again:
cifs_sb->rsize = cifs_negotiate_rsize(tcon, volume_info);
/* tune readahead according to rsize */
cifs_sb->bdi.ra_pages = cifs_ra_pages(cifs_sb);
cifs_sb->bdi.ra_pages = cifs_sb->rsize / PAGE_CACHE_SIZE;
remote_path_check:
#ifdef CONFIG_CIFS_DFS_UPCALL