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Commit 8f71465c authored by Jeff Layton's avatar Jeff Layton Committed by Steve French
Browse files

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



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: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarSteve French <sfrench@us.ibm.com>
parent 156d1790

fs/cifs/connect.c

+1 −17
Original line number Diff line number Diff line
@@ -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 @@ cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *volume_info) 
	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