imposing memory limits in FreeBSD 8

[Artem Belevich]

On Sat, Apr 9, 2011 at 10:15 AM, Joe Schaefer <joesuf4 at gmail.com> wrote:
> While I am thrilled about the newfound zfs stability that upgrading to 8
> has brought, one of the things that seems to have been dropped is
> support for process memory limits.  I have a few servers that occasionally
> run out of swap due to runaway httpd daemons, and the ulimit -m settings
> in the startup scripts we use stopped working upon upgrading from FreeBSD 6.
>
> I've tried fiddling with the daemon class in login.conf to no avail
> either.  About
> the only thing I haven't tried is running httpd under djb's softlimit
> executable.
> Here's my daemon class in login.conf:
>
> daemon:\
>        :memoryuse=1g:\
>        :datasize=1g:\
>        :stacksize=1g:\
>        :tc=default:
>
> and proof that `limits` groks the config:
>
> # limits -eHC daemon
> ulimit -t unlimited;
> ulimit -f unlimited;
> ulimit -d 1048576;
> ulimit -s 1048576;
> ulimit -c unlimited;
> ulimit -m 1048576;
> ulimit -l unlimited;
> ulimit -u unlimited;
> ulimit -n unlimited;
> ulimit -b unlimited;
> ulimit -v unlimited;
> ulimit -p unlimited;
> ulimit -w unlimited;
>
> Any tips from admins who have successfully imposed memory constraints in 8.x?

If I recall it correctly, in -8 malloc defaults to mmap for memory
allocations, so RLIMIT_DATA no longer applies.
You have to set RLIMIT_VMEM, but be careful as that would include
everything mmapped in even if it does not use much of that. rpc.statd
is one example of that -- it mmaps in ~256M but has only ~400K
resident set size.

Another option would be to make malloc() switch back to  sbrk() with
MALLOC_OPTIONS=D. This way datasize limit will still be in effect.

--Artem