linux-kernel - Re: [RFC PATCH 0/4] sched+mm: Track lazy active mm existence with hazard pointers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Zv1n0VeM3ZSVPyyE@casper.infradead.org>
Date: Wed, 2 Oct 2024 16:33:37 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: paulmck@...nel.org, Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org,
	Nicholas Piggin <npiggin@...il.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Will Deacon <will@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	John Stultz <jstultz@...gle.com>,
	Neeraj Upadhyay <Neeraj.Upadhyay@....com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>, Ingo Molnar <mingo@...hat.com>,
	Waiman Long <longman@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vlastimil Babka <vbabka@...e.cz>, maged.michael@...il.com,
	Mateusz Guzik <mjguzik@...il.com>,
	Jonas Oberhauser <jonas.oberhauser@...weicloud.com>,
	rcu@...r.kernel.org, linux-mm@...ck.org, lkmm@...ts.linux.dev
Subject: Re: [RFC PATCH 0/4] sched+mm: Track lazy active mm existence with
 hazard pointers

On Wed, Oct 02, 2024 at 11:26:27AM -0400, Mathieu Desnoyers wrote:
> On 2024-10-02 16:09, Paul E. McKenney wrote:
> > On Tue, Oct 01, 2024 at 09:02:01PM -0400, Mathieu Desnoyers wrote:
> > > Hazard pointers appear to be a good fit for replacing refcount based lazy
> > > active mm tracking.
> > > 
> > > Highlight:
> > > 
> > > will-it-scale context_switch1_threads
> > > 
> > > nr threads (-t)     speedup
> > >      24                +3%
> > >      48               +12%
> > >      96               +21%
> > >     192               +28%
> > 
> > Impressive!!!
> > 
> > I have to ask...  Any data for smaller numbers of CPUs?
> 
> Sure, but they are far less exciting ;-)

How many CPUs in the system under test?

> nr threads (-t)     speedup
>      1                -0.2%
>      2                +0.4%
>      3                +0.2%
>      6                +0.6%
>     12                +0.8%
>     24                +3%
>     48               +12%
>     96               +21%
>    192               +28%
>    384                +4%
>    768                -0.6%
> 
> Thanks,
> 
> Mathieu
> 
> > 
> > 							Thanx, Paul
> > 
> > > I'm curious to see what the build bots have to say about this.
> > > 
> > > This series applies on top of v6.11.1.
> > > 
> > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> > > Cc: Nicholas Piggin <npiggin@...il.com>
> > > Cc: Michael Ellerman <mpe@...erman.id.au>
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> > > Cc: "Paul E. McKenney" <paulmck@...nel.org>
> > > Cc: Will Deacon <will@...nel.org>
> > > Cc: Boqun Feng <boqun.feng@...il.com>
> > > Cc: Alan Stern <stern@...land.harvard.edu>
> > > Cc: John Stultz <jstultz@...gle.com>
> > > Cc: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
> > > Cc: Boqun Feng <boqun.feng@...il.com>
> > > Cc: Frederic Weisbecker <frederic@...nel.org>
> > > Cc: Joel Fernandes <joel@...lfernandes.org>
> > > Cc: Josh Triplett <josh@...htriplett.org>
> > > Cc: Uladzislau Rezki <urezki@...il.com>
> > > Cc: Steven Rostedt <rostedt@...dmis.org>
> > > Cc: Lai Jiangshan <jiangshanlai@...il.com>
> > > Cc: Zqiang <qiang.zhang1211@...il.com>
> > > Cc: Ingo Molnar <mingo@...hat.com>
> > > Cc: Waiman Long <longman@...hat.com>
> > > Cc: Mark Rutland <mark.rutland@....com>
> > > Cc: Thomas Gleixner <tglx@...utronix.de>
> > > Cc: Vlastimil Babka <vbabka@...e.cz>
> > > Cc: maged.michael@...il.com
> > > Cc: Mateusz Guzik <mjguzik@...il.com>
> > > Cc: Jonas Oberhauser <jonas.oberhauser@...weicloud.com>
> > > Cc: rcu@...r.kernel.org
> > > Cc: linux-mm@...ck.org
> > > Cc: lkmm@...ts.linux.dev
> > > 
> > > Mathieu Desnoyers (4):
> > >    compiler.h: Introduce ptr_eq() to preserve address dependency
> > >    Documentation: RCU: Refer to ptr_eq()
> > >    hp: Implement Hazard Pointers
> > >    sched+mm: Use hazard pointers to track lazy active mm existence
> > > 
> > >   Documentation/RCU/rcu_dereference.rst |  38 ++++++-
> > >   Documentation/mm/active_mm.rst        |   9 +-
> > >   arch/Kconfig                          |  32 ------
> > >   arch/powerpc/Kconfig                  |   1 -
> > >   arch/powerpc/mm/book3s64/radix_tlb.c  |  23 +---
> > >   include/linux/compiler.h              |  63 +++++++++++
> > >   include/linux/hp.h                    | 154 ++++++++++++++++++++++++++
> > >   include/linux/mm_types.h              |   3 -
> > >   include/linux/sched/mm.h              |  71 +++++-------
> > >   kernel/Makefile                       |   2 +-
> > >   kernel/exit.c                         |   4 +-
> > >   kernel/fork.c                         |  47 ++------
> > >   kernel/hp.c                           |  46 ++++++++
> > >   kernel/sched/sched.h                  |   8 +-
> > >   lib/Kconfig.debug                     |  10 --
> > >   15 files changed, 346 insertions(+), 165 deletions(-)
> > >   create mode 100644 include/linux/hp.h
> > >   create mode 100644 kernel/hp.c
> > > 
> > > -- 
> > > 2.39.2
> 
> -- 
> Mathieu Desnoyers
> EfficiOS Inc.
> https://www.efficios.com
> 
>