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Re: task blocked for more than 120 seconds

To: "Josef 'Jeff' Sipek" <jeffpc@xxxxxxxxxxxxxx>
Subject: Re: task blocked for more than 120 seconds
From: Ben Myers <bpm@xxxxxxx>
Date: Wed, 18 Apr 2012 13:28:55 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120418151139.GC4652@xxxxxxxxxxxxxxxxxxxxxx>
References: <20120418151139.GC4652@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.20 (2009-06-14)
Hey Josef,

On Wed, Apr 18, 2012 at 11:11:40AM -0400, Josef 'Jeff' Sipek wrote:
> Greetings!  I have a file server that get a pretty nasty load (about 15
> million files created every day).  After some time, I noticed that the load
> average spiked up from the usual 30 to about 180.  dmesg revealed:
> 
> [434042.318401] INFO: task php:2185 blocked for more than 120 seconds.
> [434042.318403] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables 
> this message.
> [434042.318405] php             D 000000010675d6cd     0  2185  27306 
> 0x00000000
> [434042.318408]  ffff88008d735a48 0000000000000086 ffff88008d735938 
> ffffffff00000000
> [434042.318412]  ffff88008d734010 ffff88000e28e340 0000000000012000 
> ffff88008d735fd8
> [434042.318416]  ffff88008d735fd8 0000000000012000 ffff8807ef9966c0 
> ffff88000e28e340
> [434042.318419] Call Trace:
> [434042.318442]  [<ffffffffa0087a9b>] ? xfs_trans_brelse+0xee/0xf7 [xfs]
> [434042.318464]  [<ffffffffa00689de>] ? xfs_da_brelse+0x71/0x96 [xfs]
> [434042.318485]  [<ffffffffa006df10>] ? xfs_dir2_leaf_lookup_int+0x211/0x225 
> [xfs]
> [434042.318489]  [<ffffffff8141481e>] schedule+0x55/0x57
> [434042.318512]  [<ffffffffa0083de2>] xlog_reserveq_wait+0x115/0x1c0 [xfs]
> [434042.318515]  [<ffffffff810381f1>] ? try_to_wake_up+0x23d/0x23d
> [434042.318539]  [<ffffffffa0083f45>] xlog_grant_log_space+0xb8/0x1be [xfs]
> [434042.318562]  [<ffffffffa0084164>] xfs_log_reserve+0x119/0x133 [xfs]
> [434042.318585]  [<ffffffffa0080cf1>] xfs_trans_reserve+0xca/0x199 [xfs]
> [434042.318605]  [<ffffffffa00500dc>] xfs_create+0x18d/0x467 [xfs]
> [434042.318623]  [<ffffffffa00485be>] xfs_vn_mknod+0xa0/0xf9 [xfs]
> [434042.318640]  [<ffffffffa0048632>] xfs_vn_create+0xb/0xd [xfs]
> [434042.318644]  [<ffffffff810f0c5d>] vfs_create+0x6e/0x9e
> [434042.318647]  [<ffffffff810f1c5e>] do_last+0x302/0x642
> [434042.318651]  [<ffffffff810f2068>] path_openat+0xca/0x344
> [434042.318654]  [<ffffffff810f23d1>] do_filp_open+0x38/0x87
> [434042.318658]  [<ffffffff810fb22e>] ? alloc_fd+0x76/0x11e
> [434042.318661]  [<ffffffff810e40b1>] do_sys_open+0x10b/0x1a4
> [434042.318664]  [<ffffffff810e4173>] sys_open+0x1b/0x1d
> 
> It makes sense that'd the load average would spike up if some major lock got
> held longer than it should have been.
> 
> The box has 32GB RAM, 6 cores, and it's running 3.2.2.
> 
> I've looked at the commits in the stable tree since 3.2.2 was tagged, and I
> do see a couple of useful commits so I'll try to get the kernel updated
> anyway but I don't quite see any of those fixes addressing this "hang".

I was about to suggest that 9f9c19e 'xfs: fix the logspace waiting algorithm'
is probably what you need... but that's already in 3.2.2.  Hrm.

-Ben

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