Re: [PATCH 2.6.20-rc1 00/10] Kernel memory leak detector 0.13

From: Catalin Marinas
Date: Wed Dec 27 2006 - 08:53:06 EST

On 18/12/06, Ingo Molnar <mingo@xxxxxxx> wrote:
* Catalin Marinas <catalin.marinas@xxxxxxxxx> wrote:
> I could also use a simple allocator based on alloc_pages [...]
> [...] It could be so simple that it would never need to free any
> pages, just grow the size as required and reuse the freed memleak
> objects from a list.

sounds good to me. Please make it a per-CPU pool. We'll have to fix the
locking too, to be per-CPU - memleak_lock is quite a scalability problem
right now. (Add a memleak_object->cpu pointer so that freeing can be
done on any other CPU as well.)

I did some simple statistics about allocations happening on one CPU
and freeing on a different one. On a 4-CPU ARM system (and without IRQ
balancing and without CONFIG_PREEMPT), these seem to happen in about
8-10% of the cases. Do you expect higher figures on other

As I mentioned in a different e-mail, a way to remove the global hash
table is to create per-cpu hashes. The only problem is that in these
8-10% of the cases, freeing would need to look up the other hashes.
This would become a problem with a high number of CPUs but I'm not
sure whether it would overtake the performance issues introduced by
cacheline ping-ponging in the single-hash case.

Any thoughts?


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