linux-kernel - Re: [PATCH 35/40] lib: implement context capture support for tagged allocations

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Date:   Fri, 5 May 2023 10:40:19 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
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Subject: Re: [PATCH 35/40] lib: implement context capture support for tagged
 allocations

On Thu 04-05-23 09:22:07, Suren Baghdasaryan wrote:
[...]
> > But even then I really detest an additional allocation from this context
> > for every single allocation request. There GFP_NOWAIT allocation for
> > steckdepot but that is at least cached and generally not allocating.
> > This will allocate for every single allocation.
> 
> A small correction here. alloc_tag_create_ctx() is used only for
> allocations which we requested to capture the context. So, this last
> sentence is true for allocations we specifically marked to capture the
> context, not in general.

Ohh, right. I have misunderstood that part. Slightly better, still
potentially a scalability issue because hard to debug memory leaks
usually use a generic caches (for kmalloc). So this might be still a lot
of objects to track.

> > There must be a better way.
> 
> Yeah, agree, it would be good to avoid allocations in this path. Any
> specific ideas on how to improve this? Pooling/caching perhaps? I
> think kmem_cache does some of that already but maybe something else?

The best I can come up with is a preallocated hash table to store
references to stack depots with some additional data associated. The
memory overhead could be still quite big but the hash tables could be
resized lazily.
-- 
Michal Hocko
SUSE Labs