[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]
Re: netbsd-6: pagedaemon freeze when low on memory
On 2013-03-04 16:10, Lars Heidieker wrote:
> On 2013-03-04 20:43, Richard Hansen wrote:
>> I believe I have found a bug in the pagedaemon (uvm_pageout() in
>> src/sys/uvm/uvm_pdaemon.c) that causes the system to freeze when
>> the kmem_arena runs low (<10% free):
> if you increase kern.maxvnodes a lot you need to increase the kmem
> allowed in order to accommodate all the vnodes.
> Try recompiling a kernel with NKMEMPAGES_MAX option set higher then
> the default (360mb on i386) eg 450mb.
Ah, that's good to know, thanks! I'll turn up NKMEMPAGES_MAX.
But, isn't this a bug regardless of the values of kern.maxvnodes and
NKMEMPAGES_MAX? Shouldn't the pagedaemon not freeze under memory pressure?
Some background: Turning up kern.maxvnodes is just a convenient way to
demonstrate the freeze on an unmodified NetBSD kernel. I first
encountered this freeze in a custom kernel that kmem_alloc()s a lot more
memory than an unmodified NetBSD kernel. I'll turn up NKMEMPAGES_MAX in
the custom kernel, but it'd still be desirable if the kernel handled
out-of-memory conditions more gracefully.
If an iteration in the pagedaemon doesn't free anything, perhaps
kmem_alloc(size, KM_SLEEP) should return NULL? Or maybe the kernel
should panic()? Maybe the pagedaemon should ask other subsystems (e.g.,
vnode cache) to free some memory?
Main Index |
Thread Index |