On Thu, May 15, 2008 at 10:07:14PM -0400, Ted Unangst wrote:

quoted text
> On 5/15/08, Kevin  wrote:

> > All,

> >

> >  I'm getting quite a lot of these errors in /var/log/messages and can't

> >  seem to find an appropriate fix in the archives:

> >

> >      May 14 21:05:54 svr02 /bsd: uvm_mapent_alloc: out of static map entries

> >      May 14 21:57:47 svr02 /bsd: uvm_mapent_alloc: out of static map entries

> >      May 14 23:00:05 svr02 /bsd: uvm_mapent_alloc: out of static map entries

> >      May 15 07:27:53 svr02 /bsd: uvm_mapent_alloc: out of static map entries

> >      May 15 07:39:59 svr02 /bsd: uvm_mapent_alloc: out of static map entries

> >

> >  N.B. This machine serves mirror content for various F/OSS projects in

> >  addition to standard www content, so it quite often has >350 users

> >  concurrently connected downloading mirrored content (in addition to

> >  visitors who're actually visiting the site).

>

> Are you using squid as well?  You may try doing something like

> restarting apache.

>

> The problem seems related to certain long running processes with

> fragmented address spaces.

>

> Basically, in order to manage address spaces, the kernel keeps track

> of a bunch of maps.  Entries in these maps are stored in... map

> entries.  In certain situations, the kernel can't wait to allocate a

> map entry, so it grabs one from a static list.  Previously, when they

> ran out, the kernel paniced.  Now it just says uh oh.  The kernel will

> merrily go on making more static entries as needed.

the problem is not in the user land.

the problem is in i386 pmap which abuses kmem_map that is there

for malloc(9)s use and allocates pv_entries from it.

this leads to enormous kmem_map fragmentation and unaccounted

allocations that does not show up in the vmstat and as well leads

to livelocks (sleeping on kmem_map) and out of space in kmem_map

panics as well. there is a number of measures to remediate the

situation proper

- convert pv_entries allocations to pool (i have a diff if you wanna)

- backend malloc w/ pool (filed in sendbug)

- a number of uvm fixes (such as amap ops) that reduce fragmentation.

cu

--

    paranoic mickey       (my employers have changed but, the name has remained)