Hi All If I understand it correctly, there are three points at which linux nfs client sends the NFS write request: 1. Inside nfs_flush_incompatible() where it needs to send writes as stable because the pages are required for new write request from an application. I think this happens only in case of high memory pressure. 2. Inside nfs_file_write(), when nfs_do_fsync() is called if the file was opened with O_SYNC. 3. When the file is closed, any remaining writes are flushed out as unstable and then the final commit is sent. In some of the tests I am running, I see drastic fall in write throughput between a record size(.. i.e. the size of the buffer handed to the write() syscall..) of 32Kbytes and a record size of say 50 Mbytes and 100 Mbytes. This fall is seen for NFS wsize values of 32k, 64k, 1Mb and with different tcp_slot_table_entries values of 16, 64, 96 and 128. The test files are opened without O_SYNC over a sync mounted NFS. The client is a big machine with 16 logical processors and 16Gigs of RAM. I suspect that the fall happens because the NFS client stack sends all the NFS writes as unstable till the file gets closed, when it sends the final commit request. Since the write() record sizes are pretty big the throughput drops because the final commit takes extra-ordinarily long for the whole 100Megs to commit at the server resulting in lower aggregate throughput. Is this understanding correct? Can this behaviour be modified so that the client uses the knowledge of the write() buffer size, by initiating writeback before the full 100megs needs to be committed to the server in one go? Thanks Shehjar -- 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
