Date: Sun, 13 Apr 2008 00:58:15 +0300 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: freebsd@sopwith.solgatos.com Cc: freebsd-questions@freebsd.org Subject: Re: 6.2 -> 7.0 now mlock(2) fails Message-ID: <87zlry7n2g.fsf@kobe.laptop> References: <200804122051.UAA06080@sopwith.solgatos.com>
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On Sat, 12 Apr 2008 13:51:16 +0100, Dieter <freebsd@sopwith.solgatos.com> wrote:
>> > I never saw mlock(2) fail in 6.2 but with 7.0 I sometimes
>> > get mlock(2) failed: Resource temporarily unavailable.
>>
>> That's error EAGAIN:
>>
>> [EAGAIN] Locking the indicated range would exceed
>> either the system or per-process limit
>> for locked memory.
>>
>> You are hitting either the `vm.max_wired' limit, or the per-process
>> RLIMIT_MEMLOCK limit.
>>
>> > What changed and how do I fix it?
>>
>> It would be nice if you could run a test program that prints the value of
>> vm.max_wired and RLIMIT_MEMLOCK on 6.2 and then on 7.0. As an extra test,
>> it may be worth printing these values in the log of your application when
>> mlock(2) fails.
>
> vm.max_wired looks like a sysctl, but sysctl doesn't know about it.
> sysctl: unknown oid 'vm.max_wired'
Yes, indeed. I posted before looking at the diffs between RELENG_7 and
CURRENT. The sysctl is only present in 8.0-CURRENT:
,-----------------------------------------------------------------------
| $ pwd
| /ws/bsd/src/sys/vm
| $ cvs -qR di -u -r RELENG_7 vm_pageout.c | more
| [...]
| int vm_page_max_wired; /* XXX max # of wired pages system-wide
| */
| +SYSCTL_INT(_vm, OID_AUTO, max_wired,
| + CTLFLAG_RW, &vm_page_max_wired, 0, "System-wide limit to wired page count");
`-----------------------------------------------------------------------
The max wired page count is initialized to 1/3 of the free page count in
the pageout daemon.
> sysctl -a | grep -i wire | grep -vi firewire
> vm.stats.vm.v_wire_count: 89046
>
> /usr/include/sys/resource.h:#define RLIMIT_MEMLOCK 6 /* locked-in-memory address space */
>
> It doesn't always fail, just sometimes. It is trying to lock 172490752 bytes.
> There can be two processes wanting to do this at once. Seems to be the 2nd
> one that sometimes fails.
>
> with one process:
> vm.stats.vm.v_wire_count: 130992 (41946 more)
>
> with two processes (mlock failed):
> vm.stats.vm.v_wire_count: 131047 (55 more)
>
> killed both proceses:
> vm.stats.vm.v_wire_count: 88788
Can you run your first process, which successfully wires the pages, and
then capture the output of:
sysctl vm.stats
Finally, run the second process, even if it fails to wire the pages, and
capture vm.stats once more.
PS: Please Cc: me in any responces. I may not see your message if it
gets lots in the `noise' of a busy list like -questions. I *do* try to
respond to messages which hit my INBOX, though :)
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