Messages in this thread | | | From | Toke Høiland-Jørgensen <> | Subject | Re: [PATCH net-next] page_pool: disable direct recycling based on pool->cpuid on destroy | Date | Thu, 15 Feb 2024 14:29:03 +0100 |
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Alexander Lobakin <aleksander.lobakin@intel.com> writes:
> From: Toke Høiland-Jørgensen <toke@redhat.com> > Date: Thu, 15 Feb 2024 13:05:30 +0100 > >> Alexander Lobakin <aleksander.lobakin@intel.com> writes: >> >>> Now that direct recycling is performed basing on pool->cpuid when set, >>> memory leaks are possible: >>> >>> 1. A pool is destroyed. >>> 2. Alloc cache is emptied (it's done only once). >>> 3. pool->cpuid is still set. >>> 4. napi_pp_put_page() does direct recycling basing on pool->cpuid. >>> 5. Now alloc cache is not empty, but it won't ever be freed. >> >> Did you actually manage to trigger this? pool->cpuid is only set for the >> system page pool instance which is never destroyed; so this seems a very >> theoretical concern? > > To both Lorenzo and Toke: > > Yes, system page pools are never destroyed, but we might latter use > cpuid in non-persistent PPs. Then there will be memory leaks. > I was able to trigger this by creating bpf/test_run page_pools with the > cpuid set to test direct recycling of live frames. > >> >> I guess we could still do this in case we find other uses for setting >> the cpuid; I don't think the addition of the READ_ONCE() will have any >> measurable overhead on the common arches? > > READ_ONCE() is cheap, but I thought it's worth mentioning in the > commitmsg anyway :)
Right. I'm OK with changing this as a form of future-proofing if we end up finding other uses for setting the cpuid field, so:
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
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