Re: tracking memory usage/leak in "inactive" field in /proc/meminfo?

[Rik van Riel <riel@redhat.com>]

On 02/11/2010 01:54 PM, Chris Friesen wrote:
> On 02/10/2010 06:45 PM, Minchan Kim wrote:
>> On Thu, Feb 11, 2010 at 2:05 AM, Chris Friesen<cfriesen@nortel.com>  wrote:
>
>>> In those spreadsheets I notice that
>>> memfree+active+inactive+slab+pagetables is basically a constant.
>>> However, if I don't use active+inactive then I can't make the numbers
>>> add up.  And the difference between active+inactive and
>>> buffers+cached+anonpages+dirty+mapped+pagetables+vmallocused grows
>>> almost monotonically.
>>
>> Such comparison is not right. That's because code pages of program account
>> with cached and mapped but they account just one in lru list(active +
>> inactive).
>> Also, if you use mmap on any file, above is applied.
>
> That just makes the comparison even worse...it means that there is more
> memory in active/inactive that isn't accounted for in any other category
> in /proc/meminfo.

Which does not happen in the standard 2.6.27 kernel.

Are you leaking memory in your driver?

>
>> I can't find any clue with your attachment.
>> You said you used kernel with some modification and non-vanilla drivers.
>> So I suspect that. Maybe kernel memory leak?
>
> Possibly.  Or it could be a use case issue, I know there have been
> memory leaks fixed since 2.6.27. :)
>
>> Now kernel don't account kernel memory allocations except SLAB.
>
> I don't think that's entirely accurate.  I think cached, buffers,
> pagetables, vmallocUsed are all kernel allocations.  Granted, they're
> generally on behalf of userspace.
>
> I've discovered that the generic page allocator (alloc_page, etc.) is
> not tracked at all in /proc/meminfo.  I seem to see the memory increase
> in the page cache (that is, active/inactive), so that would seem to rule
> out most direct allocations.
>
>> I think this patch can help you find the kernel memory leak.
>> (It isn't merged with mainline by somewhy but it is useful to you :)
>>
>> http://marc.info/?l=linux-mm&m=123782029809850&w=2
>
> I have a modified version of that which I picked up as part of the
> kmemleak backport.  However, it doesn't help unless I can narrow down
> *which* pages I should care about.
>
> I tried using kmemleak directly, but it didn't find anything.  I've also
> tried checking for inactive pages which haven't been written to in 10
> minutes, and haven't had much luck there either.  But active/inactive
> keeps growing, and I don't know why.
>
> Chris


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