Date: Thu, 13 Nov 2008 15:00:56 -0800 From: Chris Pratt <eagletree@hughes.net> To: FreeBSD-Questions Questions <freebsd-questions@freebsd.org> Subject: Re: 128 Bucket Failures? Message-ID: <CFB7CD2B-77E6-47D6-AE65-004457D20761@hughes.net> In-Reply-To: <gfi6hk$6u8$2@ger.gmane.org> References: <F349C4D5-EC11-4138-8D7F-17CD6C1A3C8B@hughes.net> <gfi6hk$6u8$2@ger.gmane.org>
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On Nov 13, 2008, at 1:34 PM, Ivan Voras wrote: > Chris Pratt wrote: >> I have asked this before a couple of years ago but received no >> replies. I assumed that's because it's a somewhat obscure question. >> I'm still interested and thought I might try again in case someone >> new is watching this list who might know. >> >> A vmstat -z on my highest traffic server always shows the failures >> as below on 128 Bucket. It also goes to having 0 free rather soon >> after the system is restarted and never returns to having more than >> 1 free in that column and yet always has the highest number of >> requests by far. Does this mean anything significant? Is it >> something I should tune or even can be tuned? > > UMA buckets seem to be some kind of cache for SMP-optimized > allocations > - I hope someone who knows it better will explain them. > >> Here is the output of the vmstat -z with everything chopped out >> besides the 128 Bucket line. The machine it's on is an 8 core 8 GB >> Tyan and shouldn't really be starved for anything in my way of >> thinking. >> >> vmstat -z >> ITEM SIZE LIMIT USED FREE >> REQUESTS FAILURES >> >> 128 Bucket: 1048, 0, 2043, 0, >> 13591, 6511069 > > What is the server used for? > A busy webserver (about 5G Views a month, average view is 3-4 hits). Not really large pages, we keep graphics minimal. It's apache, perl cgi, mysqld. Tends to collect a lot of garbage traffic attacks on top of real traffic, both TCP and UDP. > Here's a snapshot from a very loaded apache+php+pgsql web server, > uptime > 60 days (since the last power outage): > > 16 Bucket: 76, 0, 42, 58, 125, > 0 > 32 Bucket: 140, 0, 76, 64, 183, > 0 > 64 Bucket: 268, 0, 74, 38, 438, > 11 > 128 Bucket: 524, 0, 2060, 642, 788828, > 6985 > > A generic advice would be to increase vm.kmem_size (you're using > AMD64, > right?) and see what happens. > I'll try that. I had heard this before in relation to KVA but have been concerned about trying it. If I can just change that knob and have an effect, seems worth a try. If more than one person is doing it, it must be safe? Yes, AMD64. Thank you very much.
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