Hi! I have run a test with ab running 10000 hits with a single thread loading an image with a spacing of 5 minutes of inactivity and there is still a "variation" even measurable with apache bench: Date time mean RT measured by AB 2010-09-16 02:55:12 37.033 2010-09-16 03:01:22 37.633 2010-09-16 03:07:38 37.245 2010-09-16 03:13:51 38.867 2010-09-16 03:20:20 41.326 2010-09-16 03:29:09 38.427 2010-09-16 03:40:33 40.313 2010-09-16 03:52:16 41.049 2010-09-16 04:02:12 42.100 2010-09-16 04:19:13 40.650 2010-09-16 04:36:00 37.490 2010-09-16 04:52:15 36.126 2010-09-16 05:08:16 37.390 2010-09-16 05:24:30 34.031 2010-09-16 05:40:10 30.392 2010-09-16 05:55:14 26.779 2010-09-16 06:09:42 24.118 2010-09-16 06:23:43 24.283 2010-09-16 06:37:46 24.423 2010-09-16 06:51:50 23.334 2010-09-16 07:05:44 23.633 2010-09-16 07:19:40 22.333 2010-09-16 07:33:24 21.460 2010-09-16 07:46:58 20.632 2010-09-16 08:00:25 21.047 2010-09-16 08:13:55 20.049 2010-09-16 08:27:16 18.903 2010-09-16 08:40:25 19.244 2010-09-16 08:53:37 21.181 2010-09-16 09:07:09 21.196 2010-09-16 09:20:41 19.102 2010-09-16 09:33:52 19.755 2010-09-16 09:47:10 18.674 2010-09-16 10:00:16 18.832 2010-09-16 10:13:25 17.063 2010-09-16 10:26:16 18.207 2010-09-16 10:39:18 18.328 2010-09-16 10:52:21 17.980 2010-09-16 11:05:23 17.868 2010-09-16 11:18:21 17.417 2010-09-16 11:31:16 16.421 2010-09-16 11:44:00 17.059 2010-09-16 11:56:51 17.350 2010-09-16 12:09:44 16.641 2010-09-16 12:22:31 18.211 2010-09-16 12:35:33 16.686 2010-09-16 12:48:20 17.278 2010-09-16 13:01:13 17.172 2010-09-16 13:14:05 16.528 2010-09-16 13:26:50 16.124 2010-09-16 13:39:31 16.353 2010-09-16 13:52:15 18.287 2010-09-16 14:05:18 16.728 2010-09-16 14:18:05 17.055 2010-09-16 14:30:56 17.452 2010-09-16 14:43:50 16.491 2010-09-16 14:56:35 15.851 2010-09-16 15:09:14 16.407 2010-09-16 15:21:58 15.822 2010-09-16 15:34:36 17.049 2010-09-16 15:47:27 16.052 2010-09-16 16:00:07 16.307 2010-09-16 16:12:50 16.408 2010-09-16 16:25:34 17.201 2010-09-16 16:38:26 16.686 2010-09-16 16:51:13 16.076 2010-09-16 17:03:54 17.277 2010-09-16 17:16:47 16.468 2010-09-16 17:29:32 14.842 2010-09-16 17:42:00 15.721 2010-09-16 17:54:37 15.734 2010-09-16 18:07:15 16.160 2010-09-16 18:19:56 16.131 2010-09-16 18:32:38 15.951 2010-09-16 18:45:17 14.994 2010-09-16 18:57:47 15.365 2010-09-16 19:10:21 16.774 2010-09-16 19:23:09 17.303 2010-09-16 19:36:02 16.790 2010-09-16 19:48:50 16.421 2010-09-16 20:01:34 16.380 2010-09-16 20:14:18 15.523 2010-09-16 20:26:53 16.499 2010-09-16 20:39:38 16.596 2010-09-16 20:52:24 16.116 2010-09-16 21:05:05 16.445 2010-09-16 21:17:50 15.919 2010-09-16 21:30:29 16.928 2010-09-16 21:43:18 15.841 2010-09-16 21:55:57 16.378 2010-09-16 22:08:41 17.232 2010-09-16 22:21:33 15.755 2010-09-16 22:34:11 17.264 2010-09-16 22:47:03 18.250 2010-09-16 23:00:06 18.700 2010-09-16 23:13:13 19.165 2010-09-16 23:26:25 23.088 2010-09-16 23:40:15 23.505 2010-09-16 23:54:11 22.105 2010-09-17 00:07:52 23.635 2010-09-17 00:21:48 29.841 2010-09-17 00:36:46 29.847 2010-09-17 00:51:45 31.886 2010-09-17 01:07:04 31.010 2010-09-17 01:22:14 33.142 2010-09-17 01:37:46 35.977 2010-09-17 01:53:45 38.067 2010-09-17 02:10:06 38.245 2010-09-17 02:26:29 39.521 2010-09-17 02:43:04 39.803 2010-09-17 02:59:42 34.372 2010-09-17 03:15:26 33.135 The test got done on a server sitting next to the one tested in the same network segment. Command executed: ab -n 10000 -c 1 -X <serverip>:3128 http://<hostname>/<image URL> As you can see there is still a variation even though ab is producing lots of hits/s: something like 30hits/s This is ApacheBench, Version 2.3 <$Revision: 655654 $> Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/ Licensed to The Apache Software Foundation, http://www.apache.org/ Benchmarking <hostname> [through <serverip>:3128] (be patient) Completed 1000 requests Completed 2000 requests Completed 3000 requests Completed 4000 requests Completed 5000 requests Completed 6000 requests Completed 7000 requests Completed 8000 requests Completed 9000 requests Completed 10000 requests Finished 10000 requests Server Software: Apache-Coyote/1.1 Server Hostname: <hostname> Server Port: 80 Document Path: /<image URL> Document Length: 927 bytes Concurrency Level: 1 Time taken for tests: 331.351 seconds Complete requests: 10000 Failed requests: 0 Write errors: 0 Total transferred: 13320000 bytes HTML transferred: 9270000 bytes Requests per second: 30.18 [#/sec] (mean) Time per request: 33.135 [ms] (mean) Time per request: 33.135 [ms] (mean, across all concurrent requests) Transfer rate: 39.26 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 0 0 1.8 0 130 Processing: 0 33 17.1 31 422 Waiting: 0 33 17.1 31 422 Total: 0 33 17.3 32 423 Percentage of the requests served within a certain time (ms) 50% 32 66% 40 75% 46 80% 50 90% 58 95% 60 98% 61 99% 62 100% 423 (longest request) There is also no visible change on all the requests measured. I also did an analysis of the ICAP service RT (as measured via an analysis of tcpdumps taken) and I came to the conclusion that the Request Modification time was 0.0006s and the Response modification took 0.0017s. But the image is NOT passing thru the ResponseModification (as it is delivered from Memory, and my experience shows, that with TCP_MEM_HIT the Response Modification is not "triggered") - the overall ratio between request and response modification count measured is 3:1. Any further Ideas how to improve the RT? In the meantime I will push for an upgrade to squid 3.1 Thanks, Martin > -----Original Message----- > From: Martin Sperl > Sent: Mittwoch, 15. September 2010 21:53 > To: Amos Jeffries; squid-users@xxxxxxxxxxxxxxx > Subject: RE: Strange performance effects on squid during off > peak hours > > Hi Amos! > > Thanks for your feedback. > > > Squid is still largely IO event driven. If the network IO is less than > > say 3-4 req/sec Squid can have a queue of things waiting to happen which > > get delayed a long time (hundreds of ms) waiting to be kicked off. > > Your overview seems to show that behaviour clearly. > > > > There have been some small improvements and fixes to several of the > > lagging things but I think its still there in even the latest Squid. > > Here the Hit/s statistics on this specific server for the time: > +------+-------+-------+ > | h | allHPS| cssART| > +------+-------+-------+ > | 0 | 48.34 | 0.016 | > | 1 | 49.80 | 0.015 | > | 2 | 49.01 | 0.015 | > | 3 | 47.08 | 0.018 | > | 4 | 17.34 | 0.024 | > | 5 | 4.00 | 0.042 | > | 6 | 0.52 | 0.054 | > | 7 | 9.02 | 0.034 | > | 8 | 7.18 | 0.038 | > | 9 | 8.25 | 0.035 | > | 10 | 9.45 | 0.034 | > | 11 | 14.71 | 0.030 | > | 12 | 23.94 | 0.023 | > | 13 | 31.04 | 0.021 | > | 14 | 35.02 | 0.020 | > | 15 | 38.87 | 0.019 | > | 16 | 40.92 | 0.019 | > | 17 | 43.39 | 0.017 | > | 18 | 45.62 | 0.016 | > | 19 | 47.58 | 0.017 | > | 20 | 51.91 | 0.014 | > | 21 | 53.65 | 0.014 | > | 22 | 40.87 | 0.016 | > | 23 | 47.40 | 0.016 | > +------+-------+-------+ > > So to summarize it: we need to keep the number of hits above 30 hits/s for > squid, so that we get an acceptable Response time. > > I believe it will need some convincing of management to get this assumption > tested in production ;) > > One other Question: is squid 3.1 "better" in this respect than 3.0? > > Thanks, > Martin > > This message and the information contained herein is proprietary and > confidential and subject to the Amdocs policy statement, > you may review at http://www.amdocs.com/email_disclaimer.asp This message and the information contained herein is proprietary and confidential and subject to the Amdocs policy statement, you may review at http://www.amdocs.com/email_disclaimer.asp
