Actually wdelay is the export default, and I recall the man page saying something along the lines of doing this to allow the server to coalesce writes. Somewhere else (I think in another part of this thread) it's mentioned that the server will sit for up to 10ms waiting for other writes to this export. The reality is that wdelay+FILE_SYNC = up to a 10ms delay waiting for the write RPC to come back. That being said, I would rather leave this alone so that we don't accidentally impact something else. After all, the no_wdelay export option will work around it nicely in an all-Linux environment, and file pages don't flush with FILE_SYNC on 2.6.29. ================================================================= Brian Cowan Advisory Software Engineer ClearCase Customer Advocacy Group (CAG) Rational Software IBM Software Group 81 Hartwell Ave Lexington, MA Phone: 1.781.372.3580 Web: http://www.ibm.com/software/rational/support/ Please be sure to update your PMR using ESR at http://www-306.ibm.com/software/support/probsub.html or cc all correspondence to sw_support@xxxxxxxxxx to be sure your PMR is updated in case I am not available. From: Steve Dickson <SteveD@xxxxxxxxxx> To: Neil Brown <neilb@xxxxxxx>, Greg Banks <gnb@xxxxxxxx> Cc: Brian R Cowan/Cupertino/IBM@IBMUS, linux-nfs@xxxxxxxxxxxxxxx Date: 06/05/2009 07:38 AM Subject: Re: Link performance over NFS degraded in RHEL5. -- was : Read/Write NFS I/O performance degraded by FLUSH_STABLE page flushing Brian R Cowan wrote: > Trond Myklebust <trond.myklebust@xxxxxxxxxx> wrote on 06/04/2009 02:04:58 > PM: > >> Did you try turning off write gathering on the server (i.e. add the >> 'no_wdelay' export option)? As I said earlier, that forces a delay of >> 10ms per RPC call, which might explain the FILE_SYNC slowness. > > Just tried it, this seems to be a very useful workaround as well. The > FILE_SYNC write calls come back in about the same amount of time as the > write+commit pairs... Speeds up building regardless of the network > filesystem (ClearCase MVFS or straight NFS). Does anybody had the history as to why 'no_wdelay' is an export default? As Brian mentioned later in this thread it only helps Linux servers, but that's good thing, IMHO. ;-) So I would have no problem changing the default export options in nfs-utils, but it would be nice to know why it was there in the first place... Neil, Greg?? steved. -- 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
