On Wed, 2008-06-04 at 12:40 -0400, Olga Kornievskaia wrote: > While testing NFSv4 performance over the 10GE network, we are seeing the > following behavior and would like to know if it is normal or a bug in > the client code. > > The server offers the max_write of 1M. The client mounts the server with > the "wsize" option of 1M. Yet during the write we are seeing that the > write size is at most 49K. Why does client never come close to 1M limit? I have a feeling that is due to some crap in the VM. I'm currently investigating a situation where it appears we're sending 1 COMMIT for every 1-5 32k WRITEs. This is not a policy that stems from the NFS client, so it would appear that the VM is being silly about things. I'm specially suspicious of the code in get_dirty_limits() that is setting a limit to the number of dirty pages based on the number of pages a given BDI has written out in the recent past. As far as I can see, the intention is to penalise devices that are slow writers, but in practice it doesn't do that: it penalises the devices that have the least activity. -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@xxxxxxxxxx www.netapp.com -- 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
