linux-kernel - Re: [PATCH 00/40] Memory allocation profiling

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Date:   Wed, 3 May 2023 23:33:08 -0400
From:   Kent Overstreet <kent.overstreet@...ux.dev>
To:     Tejun Heo <tj@...nel.org>
Cc:     Suren Baghdasaryan <surenb@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
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        Alexei Starovoitov <ast@...nel.org>,
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Subject: Re: [PATCH 00/40] Memory allocation profiling

On Wed, May 03, 2023 at 04:25:30PM -1000, Tejun Heo wrote:
> I see. I'm a bit skeptical about the performance angle given that the hot
> path can be probably made really cheap even with lookups. In most cases,
> it's just gonna be an extra pointer deref and a few more arithmetics. That
> can show up in microbenchmarks but it's not gonna be much. The benefit of
> going that route would be the tracking thing being mostly self contained.

The only way to do it with a single additional pointer deref would be
with a completely statically sized hash table without chaining - it'd
have to be open addressing.

More realistically you're looking at ~3 dependent loads.