readahead: fix pipeline break caused by block plug
Also, remove unnecessary block-stray-block-put-after-teardown.patch
This commit is contained in:
Dave Jones
parent
85243fee59
commit
ebc6e50a98
|
|
@ -0,0 +1,92 @@
|
|||
commit 3deaa7190a8da38453c4fabd9dec7f66d17fff67
|
||||
Author: Shaohua Li <shaohua.li@intel.com>
|
||||
Date: Fri Feb 3 15:37:17 2012 -0800
|
||||
|
||||
readahead: fix pipeline break caused by block plug
|
||||
|
||||
Herbert Poetzl reported a performance regression since 2.6.39. The test
|
||||
is a simple dd read, but with big block size. The reason is:
|
||||
|
||||
T1: ra (A, A+128k), (A+128k, A+256k)
|
||||
T2: lock_page for page A, submit the 256k
|
||||
T3: hit page A+128K, ra (A+256k, A+384). the range isn't submitted
|
||||
because of plug and there isn't any lock_page till we hit page A+256k
|
||||
because all pages from A to A+256k is in memory
|
||||
T4: hit page A+256k, ra (A+384, A+ 512). Because of plug, the range isn't
|
||||
submitted again.
|
||||
T5: lock_page A+256k, so (A+256k, A+512k) will be submitted. The task is
|
||||
waitting for (A+256k, A+512k) finish.
|
||||
|
||||
There is no request to disk in T3 and T4, so readahead pipeline breaks.
|
||||
|
||||
We really don't need block plug for generic_file_aio_read() for buffered
|
||||
I/O. The readahead already has plug and has fine grained control when I/O
|
||||
should be submitted. Deleting plug for buffered I/O fixes the regression.
|
||||
|
||||
One side effect is plug makes the request size 256k, the size is 128k
|
||||
without it. This is because default ra size is 128k and not a reason we
|
||||
need plug here.
|
||||
|
||||
Vivek said:
|
||||
|
||||
: We submit some readahead IO to device request queue but because of nested
|
||||
: plug, queue never gets unplugged. When read logic reaches a page which is
|
||||
: not in page cache, it waits for page to be read from the disk
|
||||
: (lock_page_killable()) and that time we flush the plug list.
|
||||
:
|
||||
: So effectively read ahead logic is kind of broken in parts because of
|
||||
: nested plugging. Removing top level plug (generic_file_aio_read()) for
|
||||
: buffered reads, will allow unplugging queue earlier for readahead.
|
||||
|
||||
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
|
||||
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
|
||||
Reported-by: Herbert Poetzl <herbert@13thfloor.at>
|
||||
Tested-by: Eric Dumazet <eric.dumazet@gmail.com>
|
||||
Cc: Christoph Hellwig <hch@infradead.org>
|
||||
Cc: Jens Axboe <axboe@kernel.dk>
|
||||
Cc: Vivek Goyal <vgoyal@redhat.com>
|
||||
Cc: <stable@vger.kernel.org>
|
||||
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
||||
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
||||
|
||||
diff --git a/mm/filemap.c b/mm/filemap.c
|
||||
index 97f49ed..b662757 100644
|
||||
--- a/mm/filemap.c
|
||||
+++ b/mm/filemap.c
|
||||
@@ -1400,15 +1400,12 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
|
||||
unsigned long seg = 0;
|
||||
size_t count;
|
||||
loff_t *ppos = &iocb->ki_pos;
|
||||
- struct blk_plug plug;
|
||||
|
||||
count = 0;
|
||||
retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
|
||||
if (retval)
|
||||
return retval;
|
||||
|
||||
- blk_start_plug(&plug);
|
||||
-
|
||||
/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
|
||||
if (filp->f_flags & O_DIRECT) {
|
||||
loff_t size;
|
||||
@@ -1424,8 +1421,12 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
|
||||
retval = filemap_write_and_wait_range(mapping, pos,
|
||||
pos + iov_length(iov, nr_segs) - 1);
|
||||
if (!retval) {
|
||||
+ struct blk_plug plug;
|
||||
+
|
||||
+ blk_start_plug(&plug);
|
||||
retval = mapping->a_ops->direct_IO(READ, iocb,
|
||||
iov, pos, nr_segs);
|
||||
+ blk_finish_plug(&plug);
|
||||
}
|
||||
if (retval > 0) {
|
||||
*ppos = pos + retval;
|
||||
@@ -1481,7 +1482,6 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
|
||||
break;
|
||||
}
|
||||
out:
|
||||
- blk_finish_plug(&plug);
|
||||
return retval;
|
||||
}
|
||||
EXPORT_SYMBOL(generic_file_aio_read);
|
||||
|
|
@ -1,11 +0,0 @@
|
|||
--- linux-2.6.39.noarch/block/elevator.c~ 2011-08-09 10:07:41.532774872 -0400
|
||||
+++ linux-2.6.39.noarch/block/elevator.c 2011-08-09 10:07:56.131724173 -0400
|
||||
@@ -815,7 +815,7 @@ void elv_completed_request(struct reques
|
||||
*/
|
||||
if (blk_account_rq(rq)) {
|
||||
q->in_flight[rq_is_sync(rq)]--;
|
||||
- if ((rq->cmd_flags & REQ_SORTED) &&
|
||||
+ if ((rq->cmd_flags & REQ_SORTED) && e->ops &&
|
||||
e->ops->elevator_completed_req_fn)
|
||||
e->ops->elevator_completed_req_fn(q, rq);
|
||||
}
|
||||
|
|
@ -642,7 +642,8 @@ Patch3500: jbd-jbd2-validate-sb-s_first-in-journal_get_superblo.patch
|
|||
|
||||
Patch12016: disable-i8042-check-on-apple-mac.patch
|
||||
|
||||
Patch12026: block-stray-block-put-after-teardown.patch
|
||||
Patch12025: block-readahead-block-plug.patch
|
||||
|
||||
Patch12030: epoll-limit-paths.patch
|
||||
|
||||
Patch12303: dmar-disable-when-ricoh-multifunction.patch
|
||||
|
|
@ -1242,7 +1243,7 @@ ApplyOptionalPatch linux-2.6-v4l-dvb-experimental.patch
|
|||
ApplyPatch disable-i8042-check-on-apple-mac.patch
|
||||
|
||||
ApplyPatch epoll-limit-paths.patch
|
||||
ApplyPatch block-stray-block-put-after-teardown.patch
|
||||
ApplyPatch block-readahead-block-plug.patch
|
||||
|
||||
# rhbz#605888
|
||||
ApplyPatch dmar-disable-when-ricoh-multifunction.patch
|
||||
|
|
@ -1939,6 +1940,10 @@ fi
|
|||
# and build.
|
||||
|
||||
%changelog
|
||||
* Sun Feb 05 2012 Dave Jones <davej@redhat.com>
|
||||
- Remove unnecessary block-stray-block-put-after-teardown.patch
|
||||
- readahead: fix pipeline break caused by block plug
|
||||
|
||||
* Fri Feb 03 2012 Dave Jones <davej@redhat.com>
|
||||
- Linux 3.2.3
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue