>Number: 145229 >Category: misc >Synopsis: Vast differences in ZFS ARC behavior between 8.0-RC1 and >8.0-RELEASE >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Wed Mar 31 07:00:20 UTC 2010 >Closed-Date: >Last-Modified: >Originator: Rich Ercolani >Release: 8.0-RC1 >Organization: JHU ACM >Environment: FreeBSD manticore.acm.jhu.edu 8.0-RC1 FreeBSD 8.0-RC1 #3: Tue Sep 29 17:31:37 EDT 2009 root@:/usr/obj/usr/local/ncvs/src/sys/DTRACE amd64
>Description: Recently, I was forced back into using 8.0-RC1 temporarily when the root disk of the server failed, and we switched to an old copy of the root (we'd swapped hard drives six months ago, and had kept the old one in case of emergency). We were surprised to find that, while the pathological cases of latency were still bad, the peak performance of ZFS on 8.0-RC1 was strictly nicer than 8.0-RELEASE! In particular: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 59220 2.745 1584.125 Close 43455 2.551 1583.580 Rename 2487 5.284 1128.664 Unlink 12066 2.016 1581.133 Qpathinfo 53524 1.337 1582.991 Qfileinfo 9209 1.528 818.264 Qfsinfo 9764 2.469 545.334 Sfileinfo 4862 2.084 311.741 Find 20457 3.734 1983.271 WriteX 28984 0.051 3.099 ReadX 91122 0.638 1579.555 LockX 182 0.554 2.514 UnlockX 182 1.233 9.976 Flush 4165 7.339 1998.383 Throughput 30.3449 MB/sec 10 clients 10 procs max_latency=1998.389 ms In addition to the above numbers, we found that, more concretely, the free page count on our server was now stable at an order of magnitude higher than it had been on 8.0-RELEASE (3.1 million versus ~300k), and the ZFS ARC was now stable at approximately 1.2G (whereas on 8.0-RELEASE, regardless of how we modified the _min and _max tunables, the ARC would always stabilize at ~220M and not budge). And, concretely, while performance on non-local NFS still has horrible latency in the worst case, all of the throughput cases rapidly accelerate up from the 1-2 MB/s observed (see PR 145189) toward 8-30 MB/s, which is not ideal, but still far better than extant. I'll have a stock 8.0-RELEASE install disk for this machine within a few days, and will be able to switch between them freely for instrumenting this - but it's a fascinating....if not regression, difference in performance. >How-To-Repeat: 1) Compare local and NFS-based ZFS performance on RC1 and RELEASE >Fix: >Release-Note: >Audit-Trail: >Unformatted: _______________________________________________ freebsd-bugs@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
