Re: [PATCH] Optimize lock in queue unplugging

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From: Mike Anderson
Date: Tuesday, April 29, 2008 - 1:29 pm

Jens Axboe <jens.axboe@oracle.com> wrote:

I do not have direct access the the benchmark setup, but here is the data
I have received.

The oprofile data was showing ll_rw_blk::generic_unplug_device() as a top
routine at 13% of the samples. Annotation of the samples shows hits on
spin_lock_irq(q->queue_lock).

Here are some sample call traces:

Call trace #1

kernel:  [<ffffffff80058c6c>] generic_unplug_device+0x5d/0xc6
kernel:  [<ffffffff8820ea3e>] :dm_mod:dm_table_unplug_all+0x33/0x41
kernel:  [<ffffffff8820cc85>] :dm_mod:dm_unplug_all+0x1d/0x28
kernel:  [<ffffffff8005a78a>] blk_backing_dev_unplug+0x56/0x5b
kernel:  [<ffffffff80014cdc>] sync_buffer+0x36/0x3f
kernel:  [<ffffffff800629a4>] __wait_on_bit+0x40/0x6f
kernel:  [<ffffffff80014ca6>] sync_buffer+0x0/0x3f
kernel:  [<ffffffff80062a3f>] out_of_line_wait_on_bit+0x6c/0x78
kernel:  [<ffffffff8009c474>] wake_bit_function+0x0/0x23
kernel:  [<ffffffff88034c85>] :jbd:journal_commit_transaction+0x91f/0x1086
kernel:  [<ffffffff8003d038>] lock_timer_base+0x1b/0x3c
kernel:  [<ffffffff8803840e>] :jbd:kjournald+0xc1/0x213
kernel:  [<ffffffff8009c446>] autoremove_wake_function+0x0/0x2e
kernel:  [<ffffffff8009c283>] keventd_create_kthread+0x0/0x61
kernel:  [<ffffffff8803834d>] :jbd:kjournald+0x0/0x213
kernel:  [<ffffffff8009c283>] keventd_create_kthread+0x0/0x61
kernel:  [<ffffffff800321d5>] kthread+0xfe/0x132
kernel:  [<ffffffff8005cfb1>] child_rip+0xa/0x11
kernel:  [<ffffffff8009c283>] keventd_create_kthread+0x0/0x61
kernel:  [<ffffffff800320d7>] kthread+0x0/0x132
kernel:  [<ffffffff8005cfa7>] child_rip+0x0/0x11                       

Call trace #2
kernel:  [<ffffffff80058c6c>] generic_unplug_device+0x5d/0xc6
kernel:  [<ffffffff8820ea3e>] :dm_mod:dm_table_unplug_all+0x33/0x41
kernel:  [<ffffffff8820cc85>] :dm_mod:dm_unplug_all+0x1d/0x28
kernel:  [<ffffffff8005a78a>] blk_backing_dev_unplug+0x56/0x5b
kernel:  [<ffffffff800e8bfe>] __blockdev_direct_IO+0x889/0xaa2
kernel:  [<ffffffff88050800>] :ext3:ext3_direct_IO+0xf3/0x18b
kernel:  [<ffffffff8804ec84>] :ext3:ext3_get_block+0x0/0xe3
kernel:  [<ffffffff800be6bb>] generic_file_direct_IO+0xbd/0xfb
kernel:  [<ffffffff8001e637>] generic_file_direct_write+0x60/0xf2
kernel:  [<ffffffff80015cfd>] __generic_file_aio_write_nolock+0x2b7/0x3b8
kernel:  [<ffffffff8002134f>] generic_file_aio_write+0x65/0xc1
kernel:  [<ffffffff8804c192>] :ext3:ext3_file_write+0x16/0x91
kernel:  [<ffffffff80017944>] do_sync_write+0xc7/0x104
kernel:  [<ffffffff8009c446>] autoremove_wake_function+0x0/0x2e
kernel:  [<ffffffff80111400>] free_msg+0x22/0x3c
kernel:  [<ffffffff800161c4>] vfs_write+0xce/0x174
kernel:  [<ffffffff8004194c>] sys_pwrite64+0x50/0x70
kernel:  [<ffffffff8005cde9>] error_exit+0x0/0x84
kernel:  [<ffffffff8005c116>] system_call+0x7e/0x83

-andmike
--
Michael Anderson
andmike@linux.vnet.ibm.com
--
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Messages in current thread:
[PATCH] Optimize lock in queue unplugging, Mikulas Patocka, (Tue Apr 29, 12:12 pm)
Re: [PATCH] Optimize lock in queue unplugging, Jens Axboe, (Tue Apr 29, 12:25 pm)
Re: [PATCH] Optimize lock in queue unplugging, Mikulas Patocka, (Tue Apr 29, 1:02 pm)
Re: [PATCH] Optimize lock in queue unplugging, Jens Axboe, (Tue Apr 29, 1:05 pm)
Re: [PATCH] Optimize lock in queue unplugging, Mike Anderson, (Tue Apr 29, 1:29 pm)
Re: [PATCH] Optimize lock in queue unplugging, Jens Axboe, (Wed Apr 30, 12:14 am)
Re: [PATCH] Optimize lock in queue unplugging, Alasdair G Kergon, (Wed Apr 30, 3:38 am)
Re: [PATCH] Optimize lock in queue unplugging, Mikulas Patocka, (Wed Apr 30, 6:54 am)
Re: [PATCH] Optimize lock in queue unplugging, Jens Axboe, (Sun May 4, 12:11 pm)
Re: [PATCH] Optimize lock in queue unplugging, Mikulas Patocka, (Sun May 4, 9:01 pm)
Re: [PATCH] Optimize lock in queue unplugging, Jens Axboe, (Wed May 7, 12:45 am)