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? 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.
Description: OpenPGP digital signature