Messages in this thread | | | Date | Wed, 27 Dec 2006 13:52:46 +0000 | From | "Catalin Marinas" <> | Subject | Re: [PATCH 2.6.20-rc1 00/10] Kernel memory leak detector 0.13 |
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On 18/12/06, Ingo Molnar <mingo@elte.hu> wrote: > * Catalin Marinas <catalin.marinas@gmail.com> 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 systems/configurations?
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?
Thanks.
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