Re: requests for mbufs denied

Gabor MICSKO wrote:
Hi!

I have a relative high traffic server, running Apache, MySQL and Drupal.
With FreeBSD 6.0 and 6.1-PRERELEASE i got some distressing "netstat -m"
outputs.

Can anybody explain for me what does this message mean exactly?

"16064849/9164254/9384500 requests for mbufs denied (mbufs/clusters/mbuf
+clusters)"

And what can i do with this?

Full "netstat -m" output:

$ netstat -m
445/695/1140 mbufs in use (current/cache/total)
407/255/662/65536 mbuf clusters in use (current/cache/total/max)
407/237 mbuf+clusters out of packet secondary zone in use
(current/cache)
0/0/0/0 4k (page size) jumbo clusters in use (current/cache/total/max)
0/0/0/0 9k jumbo clusters in use (current/cache/total/max)
0/0/0/0 16k jumbo clusters in use (current/cache/total/max)
925K/683K/1609K bytes allocated to network (current/cache/total)
16064849/9164254/9384500 requests for mbufs denied (mbufs/clusters/mbuf
+clusters)
0/0/0 requests for jumbo clusters denied (4k/9k/16k)
33/964/6656 sfbufs in use (current/peak/max)
0 requests for sfbufs denied
0 requests for sfbufs delayed
56067 requests for I/O initiated by sendfile
5500 calls to protocol drain routines


Sorry for my bad english.

Thank you!



In my case, that happens when the number of free pages become less than vm.v_free_min. In such case, we drain cached buckets from zones (including mbuf zone) to the system to get more free pages, and disable bucket allocation. As the result, we cannot get a bucket when freeing a mbuf to the zone and just do internal free, counting up the number of allocation failure, i.e. the number of "requests for mbufs denied".

I don't know whether this (as to counting up the number of failure in such case) is expected or not.

--
Kazuaki Oda
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