From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
"André Almeida" <andrealmeid@igalia.com>,
"Darren Hart" <dvhart@infradead.org>,
"Davidlohr Bueso" <dave@stgolabs.net>,
"Ingo Molnar" <mingo@redhat.com>,
"Juri Lelli" <juri.lelli@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Valentin Schneider" <vschneid@redhat.com>,
"Waiman Long" <longman@redhat.com>
Subject: Re: [PATCH v8 03/15] futex: Add basic infrastructure for local task local hash.
Date: Tue, 4 Feb 2025 11:34:47 +0100 [thread overview]
Message-ID: <20250204103447.GU7145@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20250203155114.YVGnCHUT@linutronix.de>
On Mon, Feb 03, 2025 at 04:51:14PM +0100, Sebastian Andrzej Siewior wrote:
> All the things I mentioned are open for debate:
So how about we add sysctl_futex_private; when set to 0 it will disable
the private hash for every new task, unless task explicitly calls
PR_FUTEX_HASH_SET. When non-zero, it is the base for the auto-scaling.
(then BASE_SMALL would have this default to 0, otherwise 4 as per this
patch set)
I would let PR_FUTEX_HASH_SET override and disable auto-scaling. There
is nothing more annoying than a computer that thinks it knows better.
User asked for N, user gets N etc.
If user sets 0, fall back to global hash.
Anyway, none of this solves anything when a process has both an active
RT part and an active !RT part (which isn't uncommon AFAICT).
Then the RT bits will still get interference from the !RT bits. Do we
want to complicate things and consider that?
next prev parent reply other threads:[~2025-02-04 10:34 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-03 13:59 [PATCH v8 00/15] futex: Add support task local hash maps Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 01/15] rcuref: Avoid false positive "imbalanced put" report Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 02/15] futex: Create helper function to initialize a hash slot Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 03/15] futex: Add basic infrastructure for local task local hash Sebastian Andrzej Siewior
2025-02-03 14:27 ` Peter Zijlstra
2025-02-03 15:51 ` Sebastian Andrzej Siewior
2025-02-04 10:34 ` Peter Zijlstra [this message]
2025-02-05 8:39 ` Sebastian Andrzej Siewior
2025-02-07 9:41 ` Juri Lelli
2025-02-07 11:00 ` Sebastian Andrzej Siewior
2025-02-07 11:06 ` Peter Zijlstra
2025-02-07 14:47 ` Juri Lelli
2025-02-03 14:29 ` Peter Zijlstra
2025-02-03 14:41 ` Peter Zijlstra
2025-02-03 15:39 ` Peter Zijlstra
2025-02-03 15:52 ` Sebastian Andrzej Siewior
2025-02-04 8:41 ` Peter Zijlstra
2025-02-04 9:28 ` Thomas Gleixner
2025-02-03 13:59 ` [PATCH v8 04/15] futex: Allow automatic allocation of process wide futex hash Sebastian Andrzej Siewior
2025-02-03 14:36 ` Peter Zijlstra
2025-02-03 15:54 ` Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 05/15] futex: Hash only the address for private futexes Sebastian Andrzej Siewior
2025-02-03 14:41 ` Peter Zijlstra
2025-02-03 13:59 ` [PATCH v8 06/15] futex: Move private hashing into its own function Sebastian Andrzej Siewior
2025-02-04 9:34 ` Peter Zijlstra
2025-02-05 7:51 ` Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 07/15] futex: Decrease the waiter count before the unlock operation Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 08/15] futex: Prepare for reference counting of the process private hash end of operation Sebastian Andrzej Siewior
2025-02-04 9:49 ` Peter Zijlstra
2025-02-05 7:54 ` Sebastian Andrzej Siewior
2025-02-05 9:37 ` Peter Zijlstra
2025-02-03 13:59 ` [PATCH v8 09/15] futex: Re-evaluate the hash bucket after dropping the lock Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 10/15] futex: Introduce futex_get_locked_hb() Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 11/15] futex: Acquire a hash reference in futex_wait_multiple_setup() Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 12/15] futex: Allow to re-allocate the private local hash Sebastian Andrzej Siewior
2025-02-04 11:05 ` Peter Zijlstra
2025-02-05 8:00 ` Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 13/15] futex: Resize local futex hash table based on number of threads Sebastian Andrzej Siewior
2025-02-04 10:21 ` Peter Zijlstra
2025-02-05 8:05 ` Sebastian Andrzej Siewior
2025-02-07 9:07 ` Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 14/15] futex: Use a hashmask instead of hashsize Sebastian Andrzej Siewior
2025-02-03 13:59 ` [PATCH v8 15/15] futex: Avoid allocating new local hash if there is something pending Sebastian Andrzej Siewior
2025-02-04 15:14 ` [PATCH v8 00/15] futex: Add support task local hash maps Peter Zijlstra
2025-02-05 8:46 ` Sebastian Andrzej Siewior
2025-02-05 12:20 ` Sebastian Andrzej Siewior
2025-02-05 12:52 ` Peter Zijlstra
2025-02-05 16:52 ` Sebastian Andrzej Siewior
2025-02-20 15:12 ` Peter Zijlstra
2025-02-20 15:57 ` Sebastian Andrzej Siewior
2025-02-21 16:00 ` Sebastian Andrzej Siewior
2025-02-21 19:21 ` Peter Zijlstra
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