lkml.org 
[lkml]   [2006]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 28/33] readahead: loop case
Disable look-ahead for loop file.

Loopback files normally contain filesystems, in which case there are already
proper look-aheads in the upper layer, more look-aheads on the loopback file
only ruins the read-ahead hit rate.

Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---

I'd like to thank Tero Grundstr?m for uncovering the loopback problem.

drivers/block/loop.c | 6 ++++++
1 files changed, 6 insertions(+)

--- linux-2.6.17-rc4-mm3.orig/drivers/block/loop.c
+++ linux-2.6.17-rc4-mm3/drivers/block/loop.c
@@ -779,6 +779,12 @@ static int loop_set_fd(struct loop_devic
mapping = file->f_mapping;
inode = mapping->host;

+ /*
+ * The upper layer should already do proper look-ahead,
+ * one more look-ahead here only ruins the cache hit rate.
+ */
+ file->f_ra.flags |= RA_FLAG_NO_LOOKAHEAD;
+
if (!(file->f_mode & FMODE_WRITE))
lo_flags |= LO_FLAGS_READ_ONLY;

--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-05-24 13:25    [W:0.346 / U:0.524 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site