Messages in this thread | | | Date | Sat, 26 Jun 2010 14:52:22 +0200 | Subject | Re: 2.6.35-rc3 deadlocks on semaphore operations | From | Luca Tettamanti <> |
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On Fri, Jun 25, 2010 at 11:09 PM, Manfred Spraul <manfred@colorfullife.com> wrote: > On 06/24/2010 09:22 PM, Luca Tettamanti wrote: >> >> Argh, "seems" was indeed appropriate. Manfred your patch does >> alleviate the problem but something is still wrong. I noticed (I'm >> developing an ajax heavy web app) that sometimes an apache worker >> hangs; I can reproduce the problem with ab (apache benchmark) and a >> high concurrency level (I'm testing with 100 and 10k requests, and I >> get only 2-5 dropped requests). This does not happen with 2.4.34. >> Any idea on how I can debug this further? >> >> > > Are there still hung httpd processes?
They don't seem really hung as before, I see two different behaviours: * Near the end of the run ab is frozen for a few seconds, but in the end all requests are processed; however I see a few "length" errors, meaning that the received page does not match the expected content (I'm testing a static page):
Concurrency Level: 100 Time taken for tests: 14.682 seconds Complete requests: 10000 Failed requests: 10 (Connect: 0, Receive: 0, Length: 10, Exceptions: 0) Write errors: 0 Total transferred: 79987946 bytes HTML transferred: 77190466 bytes Requests per second: 681.11 [#/sec] (mean) Time per request: 146.819 [ms] (mean) Time per request: 1.468 [ms] (mean, across all concurrent requests) Transfer rate: 5320.36 [Kbytes/sec] received
Connection Times (ms) min mean[+/-sd] median max Connect: 0 1 0.4 0 3 Processing: 3 29 428.9 15 14678 Waiting: 0 15 1.3 15 19 Total: 5 30 429.0 16 14682 ERROR: The median and mean for the initial connection time are more than twice the standard deviation apart. These results are NOT reliable. Percentage of the requests served within a certain time (ms) 50% 16 66% 17 75% 17 80% 17 90% 17 95% 17 98% 18 99% 18 100% 14682 (longest request)
strace on apache shows: [pid 3787] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3789] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3788] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3784] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3783] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3782] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3239] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3233] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3238] restart_syscall(<... resuming interrupted call ...> <unfinished ...> [pid 3237] restart_syscall(<... resuming interrupted call ...>
* Sometimes ab pauses at the end but not all requests are successful; ab says:
apr_socket_recv: Connection timed out (110) Total of 9932 requests completed
The problem seems more acute if there's other application running on the system (e.g. right now I have kde, firefox, thunderbird active and I see more errors; note that nothing is using much CPU time). I've taken a sysrq-t log during one of ab pauses, it's attached.
Might be related: KDE (4.4) takes an usual amount of time to start up: the splash screen is fronzen for a while on the screen before the desktop is available (.xsession-error does not show anything interesting).
Luca PS: I'll be offline until Monday 5th... [unhandled content-type:application/x-gzip] | |