linux-kernel - Re: [RFC v2 PATCH 0/4] futex: Add support task local hash maps.

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Message-ID: <ZyDCoduIh3yryRVB@jlelli-thinkpadt14gen4.remote.csb>
Date: Tue, 29 Oct 2024 12:10:25 +0100
From: Juri Lelli <juri.lelli@...hat.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-kernel@...r.kernel.org,
	André Almeida <andrealmeid@...lia.com>,
	Darren Hart <dvhart@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Valentin Schneider <vschneid@...hat.com>,
	Waiman Long <longman@...hat.com>
Subject: Re: [RFC v2 PATCH 0/4] futex: Add support task local hash maps.

Hi Sebastian,

On 28/10/24 13:13, Sebastian Andrzej Siewior wrote:
> Hi,
> 
> this is a follow up on
> 	https://lore.kernel.org/ZwVOMgBMxrw7BU9A@jlelli-thinkpadt14gen4.remote.csb

Thank you so much for working on this!

> and adds support for task local futex_hash_bucket. It can be created via
> prctl(). Last patch in the series enables it one the first thread is
> created.
> 
> I've been how this auto-create behaves and so far dpkg creates threads
> and uses the local-hashmap. systemd-journal on the hand forks a thread
> from time to time and I haven't seen it using the hashmap. Need to do
> more testing.

I ported it to one of our kernels with the intent of asking perf folks
to have a go at it (after some manual smoke testing maybe). It will
take a couple of weeks or so to get numbers back.

Do you need specific additional info to possibly be collected while
running? I saw your reply about usage. If you want to agree on what to
collect feel free to send out the debug patch I guess you used for that.

Going of course to also play with it myself and holler if I find any
issue.

Best,
Juri