On Sat, 2009-07-11 at 21:03 +0400, Andrey Borzenkov wrote: > Recently we have the case of very high latencies on NFS reads as > reported by application (SAP R/3). NFS server was NetApp FAS; according > to NetApp statistic, average volume read latencies were in order 10ms, > while SAP stats gave 30-50ms. Systems were interconnected by dedicated > 1Gb/s Cisco switches (3750G) with ca. 30% max load on interfaces. > > On advice of my colleague we changed sunrpc.tcp_slot_table_entries from > default 16 to 128 which seemed to make situation much better - without > changing load pattern of filer in any visible way. > > Now, I can understand, why we observed much higher latency on system and > why changing (what effectively is) queue depth helped. But I am totally > frustrated that there does not appear to be *any* possibility to detect > this situation on Linux side and to get a real numbers of real NFS IO > latencies or number of requests waiting to be executed (and I do not > even dream about per-mount point stats). > > I am grateful for any hints how can we monitor Linux NFS client and get > real-life numbers of what happens inside. Thank you! See the nfs-iostat utility in the nfs-utils package: http://git.linux-nfs.org/?p=steved/nfs-utils.git;a=blob;f=tools/nfs-iostat/nfs-iostat.py;h=9626d42609b9485c7fda0c9ef69d698f9fa929fd;hb=HEAD Trond -- 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
