On Wed, Mar 31, 2010 at 3:21 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: > On 03/31/2010 07:20 AM, Daniel J Blueman wrote: >> >> Talking of expensive, I see latencytop show>16000ms latency for >> writing pages when I have a workload that does large buffered I/O to >> an otherwise uncongested server. The gigabit network is saturated, and >> reads often stall for 1000-4000ms (!). Client has the default 16 TCP >> request slots, and server has 8 nfsds - the server is far from disk or >> processor-saturated. I'll see if there is any useful debugging I can >> get about this. > > That latency is pretty much guaranteed to be due to a long RPC backlog queue > on the client. Bumping the size of the slot table to 128 and increasing the > number of NFSD threads may help. Increasing these values did help quite a bit, though I was still seeing 5000-8000ms at nfs_wait_bit_uninterruptible() [1] and close(). Then again, I also was seeing 'Scheduler waiting for cpu' taking up to 3000ms! I suspect processor throttling, due to exceeding thermal limits. Thanks, Daniel --- [1] nfs_wait_bit_uninterruptible nfs_wait_on_request nfs_wait_in_requests_locked nfs_sync_mapping_wait nfs_write_mapping nfs_wb_nocommit nfs_getattr vfs_getattr vfs_fstat sys_newfstat system_call_fastpath -- Daniel J Blueman -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
