Messages in this thread | | | Date | Wed, 6 Apr 2005 18:01:23 +0200 | From | Jakob Oestergaard <> | Subject | bdflush/rpciod high CPU utilization, profile does not make sense |
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Hello list,
Setup; NFS server (dual opteron, HW RAID, SCA disk enclosure) on 2.6.11.6 NFS client (dual PIII) on 2.6.11.6
Both on switched gigabit ethernet - I use NFSv3 over UDP (tried TCP but this makes no difference).
Problem; during simple tests such as a 'cp largefile0 largefile1' on the client (under the mountpoint from the NFS server), the client becomes extremely laggy, NFS writes are slow, and I see very high CPU utilization by bdflush and rpciod.
For example, writing a single 8G file with dd will give me about 20MB/sec (I get 60+ MB/sec locally on the server), and the client rarely drops below 40% system CPU utilization.
I tried profiling the client (booting with profile=2), but the profile traces do not make sense; a profile from a single write test where the client did not at any time drop below 30% system time (and frequently were at 40-50%) gives me something like:
raven:~# less profile3 | sort -nr | head 257922 total 2.6394 254739 default_idle 5789.5227 960 smp_call_function 4.0000 888 __might_sleep 5.6923 569 finish_task_switch 4.7417 176 kmap_atomic 1.7600 113 __wake_up 1.8833 74 kmap 1.5417 64 kunmap_atomic 5.3333
The difference between default_idle and total is 1.2% - but I never saw system CPU utilization under 30%...
Besides, there's basically nothing in the profile that rhymes with rpciod or bdflush (the two high-hitters on top during the test).
What do I do?
Performance sucks and the profiles do not make sense...
Any suggestions would be greatly appreciated,
Thank you!
--
/ jakob
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