Re: less aggressive contigmalloc ?

On 08/24/2012 09:57, Luigi Rizzo wrote:
> On Fri, Aug 24, 2012 at 12:43:33AM -0500, Alan Cox wrote:
>> On 08/23/2012 12:45, Luigi Rizzo wrote:
>>> On Thu, Aug 23, 2012 at 12:08:40PM -0500, Alan Cox wrote:
>>> ...
>>>>> yes i do see that.
>>>>>
>>>>> Maybe less aggressive with M_NOWAIT but still kills processes.
>>>> Are you compiling world with MALLOC_PRODUCTION?  The latest version of
>>> whatever the default is. But:
>>>
>>>> jemalloc uses significantly more memory when debugging options are
>>>> enabled.  This first came up in a thread titled "10-CURRENT and swap
>>>> usage" back in June.
>>>>
>>>> Even at its most aggressive, M_WAITOK, contigmalloc() does not directly
>>>> kill processes.  If process death coincides with the use of
>>>> contigmalloc(), then it is simply the result of earlier, successful
>>>> contigmalloc() calls, or for that matter any other physical memory
>>>> allocation calls, having depleted the pool of free pages to the point
>>>> that the page daemon runs and invokes vm_pageout_oom().
>>> does it mean that those previous allocations relied on memory overbooking ?
>> Yes.
>>
>>> Is there a way to avoid that, then ?
>> I believe that malloc()'s default minimum allocation size is 4MB.  You
>> could reduce that.
>>
>> Alternatively, you can enable MALLOC_PRODUCTION.
> i tried this, and as others mentioned it makes life
> better and reduces the problem but contigmalloc still triggers
> random process kills.

I would be curious to see a stack backtrace when vm_pageout_oom() is called.