128 Bucket Failures?
eagletree at hughes.net
Thu Nov 13 15:01:16 PST 2008
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
> - 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
>> 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).
large pages, we keep graphics minimal. It's apache, perl cgi, mysqld.
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,
> 60 days (since the last power outage):
> 16 Bucket: 76, 0, 42, 58, 125,
> 32 Bucket: 140, 0, 76, 64, 183,
> 64 Bucket: 268, 0, 74, 38, 438,
> 128 Bucket: 524, 0, 2060, 642, 788828,
> A generic advice would be to increase vm.kmem_size (you're using
> right?) and see what happens.
I'll try that. I had heard this before in relation to KVA but have
about trying it. If I can just change that knob and have an effect,
a try. If more than one person is doing it, it must be safe?
Yes, AMD64. Thank you very much.
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