On Sat, Jun 23, 2012 at 08:26:04PM +0800, Fengguang Wu wrote:
> Hi,
>
> When doing parallel kernel builds on an NFSROOT system with 32 logical
> CPUs, I see half CPU time spent in kernel:
>
> top - 20:08:28 up 5:01, 8 users, load average: 62.97, 55.82, 54.56
> Tasks: 751 total, 80 running, 671 sleeping, 0 stopped, 0 zombie
> Cpu(s): 0.1%us, 53.5%sy, 46.4%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.1%si, 0.0%st
> Mem: 65401132k total, 36455604k used, 28945528k free, 0k buffers
> Swap: 0k total, 0k used, 0k free, 31858244k cached
>
> The attached lock_stat shows that rpcauth_lookup_credcache() has the
> outstanding contentions.
Aha, I got some progress: 20% kernel time can be saved when increasing
the hash bits from 4 to 10 with sunrpc.auth_hashtable_size=10:
Cpu(s): 0.0%us, 38.3%sy, 61.6%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.1%si, 0.0%st
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
class name con-bounces contentions waittime-min waittime-max waittime-total acq-bounces acquisitions holdtime-min holdtime-max holdtime-total
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
&(&dentry->d_lock)->rlock: 268601736 276206929 0.07 26627.70 496747630.48 2001328443 5557869248 0.06 37208.89 1755583747.41
-------------------------
&(&dentry->d_lock)->rlock 24861581 [<ffffffff8116de34>] unlazy_walk+0x8a/0x1bb
&(&dentry->d_lock)->rlock 148863110 [<ffffffff81177f50>] dput+0x46/0x17c
&(&dentry->d_lock)->rlock 13725203 [<ffffffff81178c3c>] __d_lookup+0xa2/0x19d
&(&dentry->d_lock)->rlock 46173902 [<ffffffff811770a9>] dget_parent+0x63/0xd5
-------------------------
&(&dentry->d_lock)->rlock 86386730 [<ffffffff811770a9>] dget_parent+0x63/0xd5
&(&dentry->d_lock)->rlock 20746860 [<ffffffff8116dd9a>] path_get+0x2c/0x3c
&(&dentry->d_lock)->rlock 12672320 [<ffffffff81178c3c>] __d_lookup+0xa2/0x19d
&(&dentry->d_lock)->rlock 32752994 [<ffffffff8116de34>] unlazy_walk+0x8a/0x1bb
...............................................................................................................................................................................................
&(&new->lock)->rlock: 230350869 230621514 0.08 6929.01 361504869.99 965086516 1052051247 0.07 5783.47 369851400.65
--------------------
&(&new->lock)->rlock 230621514 [<ffffffff81d026c0>] rpcauth_lookup_credcache+0xa7/0x244
--------------------
&(&new->lock)->rlock 230621514 [<ffffffff81d026c0>] rpcauth_lookup_credcache+0xa7/0x244
Thanks,
Fengguang
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