2015-07-18 04:29:12 +00:00
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From 63eb7031005b6f22fc1dab9f0c29435f1b52a96b Mon Sep 17 00:00:00 2001
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2015-07-03 03:40:34 +00:00
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From: Ming Lei <ming.lei@canonical.com>
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Date: Tue, 5 May 2015 19:49:55 +0800
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Subject: [PATCH 2/2] block: loop: avoiding too many pending per work I/O
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If there are too many pending per work I/O, too many
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high priority work thread can be generated so that
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system performance can be effected.
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This patch limits the max_active parameter of workqueue as 16.
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This patch fixes Fedora 22 live booting performance
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regression when it is booted from squashfs over dm
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based on loop, and looks the following reasons are
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related with the problem:
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- not like other filesyststems(such as ext4), squashfs
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is a bit special, and I observed that increasing I/O jobs
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to access file in squashfs only improve I/O performance a
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little, but it can make big difference for ext4
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- nested loop: both squashfs.img and ext3fs.img are mounted
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as loop block, and ext3fs.img is inside the squashfs
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- during booting, lots of tasks may run concurrently
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Fixes: b5dd2f6047ca108001328aac0e8588edd15f1778
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Cc: stable@vger.kernel.org (v4.0)
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Cc: Justin M. Forbes <jforbes@fedoraproject.org>
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Signed-off-by: Ming Lei <ming.lei@canonical.com>
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Acked-by: Tejun Heo <tj@kernel.org>
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Signed-off-by: Jens Axboe <axboe@fb.com>
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---
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drivers/block/loop.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/drivers/block/loop.c b/drivers/block/loop.c
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2015-07-18 04:29:12 +00:00
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index 9786aa3..cef6fa8 100644
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2015-07-03 03:40:34 +00:00
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--- a/drivers/block/loop.c
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+++ b/drivers/block/loop.c
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2015-07-18 04:29:12 +00:00
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@@ -725,7 +725,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
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2015-07-03 03:40:34 +00:00
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goto out_putf;
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error = -ENOMEM;
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lo->wq = alloc_workqueue("kloopd%d",
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- WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 0,
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+ WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 16,
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lo->lo_number);
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if (!lo->wq)
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goto out_putf;
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--
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2.4.5
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