I accidently replied to the list, so my post is in moderation, please forward it
to Rainer and kill it from the list.
David Lang
On Thu, 24 Mar 2016, Rainer Gerhards wrote:
Date: Thu, 24 Mar 2016 10:33:34 +0100
From: Rainer Gerhards <[email protected]>
Reply-To: rsyslog-users <[email protected]>
To: rsyslog-users <[email protected]>
Subject: Re: [rsyslog] possible performance regression since 8.17 and possible
memory leak in 8.17
2016-03-23 19:03 GMT+01:00 David Lang <[email protected]>:
On Fri, 18 Mar 2016, Rainer Gerhards wrote:
One thing that triggers my mind is the change of hash function. In
8.17, we use a different hash function inside libfastjson. This has
prooven to be much faster in experiments we carried out, but maybe
it's not the case for you. You can comment out line 1640
https://github.com/rsyslog/rsyslog/blob/master/tools/rsyslogd.c#L1640
here and see what happens.
that does not appear to have made any noticable difference
OK, that's more along the lines of what I thought.
Could we try to identify the bottleneck, first? I think performance
profiler data would be great. Could you run
$ valgrind --tool=cachegrind rsyslogd -n ...
on a test machine (or quickly in a terminal session on the prod
machine). A short run handling around 100k...200k messages should be
fully sufficient. It'll write a cachegrind.out.<pid> file, which you
can read for example with the kcachegrind gui tool. That will tell
where the hotspots are.
Can you send me the cachegrind file plus the git head hash from that
you build (so that I get correct source listings). That won't get me
to the point where I know sufficient details, but it'll get me started
to think about other steps. I think the next thing to do is most
probably do a testrun with json-c instead of libfastjson, just to
verify. But let's decide this once we see the baseline profile data.
Thanks,
Rainer
PS: in Germany, a long easter holiday starts tomorrow end stops next
Tuesday (so fr to mon is holiday). I'll be traveling with family, but
I'll have access to sufficiently good equipment to look into this
issue.
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