Date: Wed, 8 Aug 2012 09:51:29 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Alexey Vlasov <renton@renton.name>
Cc: Mike Galbraith <efault@gmx.de>, linux-kernel@vger.kernel.org
Subject: Re: Attaching a process to cgroups
Message-ID: <20120808165129.GG2403@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
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On Wed, Aug 08, 2012 at 08:40:33PM +0400, Alexey Vlasov wrote:
> On Wed, Jul 25, 2012 at 03:57:47PM +0200, Mike Galbraith wrote:
> > > Hanging on read():
> > > 
> > > # strace -ttT cat /proc/cgroups 
> > > 
> > > 17:30:43.825005 fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 13), ...}) = 0 <0.000005>
> > > 17:30:43.825048 open("/proc/cgroups", O_RDONLY) = 3 <0.000014>
> > > 17:30:43.825085 fstat(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0 <0.000004>
> > > 17:30:43.825125 fadvise64(3, 0, 0, POSIX_FADV_SEQUENTIAL) = 0 <0.000005>
> > > 17:30:43.825161 read(3, "#subsys_name\thierarchy\tnum_cgrou"..., 32768) = 112 <7.447084>
> 
> In general I've changed it to synchronize_rcu_expedited () and all the
> delays have gone both on writing and reading files from cgroups.

Is the writing and reading from cgroups something that your workload
does all the time, or is it something that happens only on occasional
updates to your cgroup configuration?

							Thanx, Paul

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