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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