linux-kernel - Re: [Bug #32982] Kernel locks up a few minutes after boot

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Message-ID: <4DAD5156.2050300@fusionio.com>
Date:	Tue, 19 Apr 2011 11:09:42 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Bart Van Assche <bvanassche@....org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Florian Mickler <florian@...kler.org>,
	Neil Brown <neilb@...e.de>
Subject: Re: [Bug #32982] Kernel locks up a few minutes after boot

On 2011-04-18 20:32, Bart Van Assche wrote:
> On Mon, Apr 18, 2011 at 8:28 PM, Jens Axboe <jaxboe@...ionio.com> wrote:
>> On 2011-04-18 20:21, Bart Van Assche wrote:
>>> a performance regression in the block layer not related to the md
>>> issue. If I run a small block IOPS test on a block device created by
>>> ib_srp (NOOP scheduler) I see about 11% less IOPS than with 2.6.38.3
>>> (155.000 IOPS with 2.6.38.3 and 140.000 IOPS with 2.6.39-rc3+).
>>
>> That's not good. What's the test case?
> 
> Nothing more than a fio IOPS test:
> 
> fio --bs=512 --ioengine=libaio --buffered=0 --rw=read --thread
> --iodepth=64 --numjobs=2 --loops=10000 --group_reporting --size=1G
>     --gtod_reduce=1 --name=iops-test --filename=/dev/${dev} --invalidate=1

Bart, can you try the below:

diff --git a/block/blk-core.c b/block/blk-core.c
index 5fa3dd2..9b41da1 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -307,11 +307,7 @@ void __blk_run_queue(struct request_queue *q)
 	 * Only recurse once to avoid overrunning the stack, let the unplug
 	 * handling reinvoke the handler shortly if we already got there.
 	 */
-	if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
-		q->request_fn(q);
-		queue_flag_clear(QUEUE_FLAG_REENTER, q);
-	} else
-		queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
+	q->request_fn(q);
 }
 EXPORT_SYMBOL(__blk_run_queue);
 

-- 
Jens Axboe

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