Re: less aggressive contigmalloc ?

On 08/24/2012 11:54, Luigi Rizzo wrote:
> On Fri, Aug 24, 2012 at 11:12:51AM -0500, Alan Cox wrote:
>> 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.
> you mean a backtrace of the process(es) that get killed ?

No, a backtrace showing who called vm_pageout_oom().  Simply add a 
kdb_backtrace() call at the start of vm_pageout_oom().  There are two 
possibilities.  I want to know which it is.