From 02a6b08b2706501fb0fe6ff2df2f7d8377f2f69b Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Tue, 5 May 2015 19:49:55 +0800 Subject: [PATCH 2/2] block: loop: avoiding too many pending per work I/O If there are too many pending per work I/O, too many high priority work thread can be generated so that system performance can be effected. This patch limits the max_active parameter of workqueue as 16. This patch fixes Fedora 22 live booting performance regression when it is booted from squashfs over dm based on loop, and looks the following reasons are related with the problem: - not like other filesyststems(such as ext4), squashfs is a bit special, and I observed that increasing I/O jobs to access file in squashfs only improve I/O performance a little, but it can make big difference for ext4 - nested loop: both squashfs.img and ext3fs.img are mounted as loop block, and ext3fs.img is inside the squashfs - during booting, lots of tasks may run concurrently Fixes: b5dd2f6047ca108001328aac0e8588edd15f1778 Cc: stable@vger.kernel.org (v4.0) Cc: Justin M. Forbes Signed-off-by: Ming Lei Acked-by: Tejun Heo Signed-off-by: Jens Axboe --- drivers/block/loop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index fec06d5..daaaf70 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -777,7 +777,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, goto out_putf; error = -ENOMEM; lo->wq = alloc_workqueue("kloopd%d", - WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 0, + WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_UNBOUND, 16, lo->lo_number); if (!lo->wq) goto out_putf; -- 2.4.5