Author: arekm Date: Sat Sep 10 19:08:08 2011 GMT
Module: packages Tag: HEAD
---- Log message:
- speedup regression issue solved
---- Files affected:
packages/kernel:
kernel-small_fixes.patch (1.35 -> 1.36)
---- Diffs:
================================================================
Index: packages/kernel/kernel-small_fixes.patch
diff -u packages/kernel/kernel-small_fixes.patch:1.35
packages/kernel/kernel-small_fixes.patch:1.36
--- packages/kernel/kernel-small_fixes.patch:1.35 Thu Sep 8 17:54:07 2011
+++ packages/kernel/kernel-small_fixes.patch Sat Sep 10 21:08:02 2011
@@ -743,3 +743,61 @@
struct xfs_ail_cursor *cur);
void xfs_trans_ail_cursor_done(struct xfs_ail *ailp,
struct xfs_ail_cursor *cur);
+commit 37b652ec6445be99d0193047d1eda129a1a315d3
+Author: Dave Chinner <[email protected]>
+Date: Thu Aug 25 07:17:01 2011 +0000
+
+ xfs: don't serialise direct IO reads on page cache checks
+
+ There is no need to grab the i_mutex of the IO lock in exclusive
+ mode if we don't need to invalidate the page cache. Taking these
+ locks on every direct IO effective serialises them as taking the IO
+ lock in exclusive mode has to wait for all shared holders to drop
+ the lock. That only happens when IO is complete, so effective it
+ prevents dispatch of concurrent direct IO reads to the same inode.
+
+ Fix this by taking the IO lock shared to check the page cache state,
+ and only then drop it and take the IO lock exclusively if there is
+ work to be done. Hence for the normal direct IO case, no exclusive
+ locking will occur.
+
+ Signed-off-by: Dave Chinner <[email protected]>
+ Tested-by: Joern Engel <[email protected]>
+ Reviewed-by: Christoph Hellwig <[email protected]>
+ Signed-off-by: Alex Elder <[email protected]>
+
+diff --git a/fs/xfs/linux-2.6/xfs_file.c b/fs/xfs/linux-2.6/xfs_file.c
+index 7f7b424..8fd4a07 100644
+--- a/fs/xfs/linux-2.6/xfs_file.c
++++ b/fs/xfs/linux-2.6/xfs_file.c
+@@ -317,7 +317,19 @@ xfs_file_aio_read(
+ if (XFS_FORCED_SHUTDOWN(mp))
+ return -EIO;
+
+- if (unlikely(ioflags & IO_ISDIRECT)) {
++ /*
++ * Locking is a bit tricky here. If we take an exclusive lock
++ * for direct IO, we effectively serialise all new concurrent
++ * read IO to this file and block it behind IO that is currently in
++ * progress because IO in progress holds the IO lock shared. We only
++ * need to hold the lock exclusive to blow away the page cache, so
++ * only take lock exclusively if the page cache needs invalidation.
++ * This allows the normal direct IO case of no page cache pages to
++ * proceeed concurrently without serialisation.
++ */
++ xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
++ if ((ioflags & IO_ISDIRECT) && inode->i_mapping->nrpages) {
++ xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
+ xfs_rw_ilock(ip, XFS_IOLOCK_EXCL);
+
+ if (inode->i_mapping->nrpages) {
+@@ -330,8 +342,7 @@ xfs_file_aio_read(
+ }
+ }
+ xfs_rw_ilock_demote(ip, XFS_IOLOCK_EXCL);
+- } else
+- xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
++ }
+
+ trace_xfs_file_read(ip, size, iocb->ki_pos, ioflags);
+
================================================================
---- CVS-web:
http://cvs.pld-linux.org/cgi-bin/cvsweb.cgi/packages/kernel/kernel-small_fixes.patch?r1=1.35&r2=1.36&f=u
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