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Wed, 2 Oct 2024 11:28:29 -0400 (EDT) Message-ID: Date: Wed, 2 Oct 2024 11:26:27 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/4] sched+mm: Track lazy active mm existence with hazard pointers To: paulmck@kernel.org Cc: Linus Torvalds , Andrew Morton , Peter Zijlstra , linux-kernel@vger.kernel.org, Nicholas Piggin , Michael Ellerman , Greg Kroah-Hartman , Sebastian Andrzej Siewior , Will Deacon , Boqun Feng , Alan Stern , John Stultz , Neeraj Upadhyay , Frederic Weisbecker , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Steven Rostedt , Lai Jiangshan , Zqiang , Ingo Molnar , Waiman Long , Mark Rutland , Thomas Gleixner , Vlastimil Babka , maged.michael@gmail.com, Mateusz Guzik , Jonas Oberhauser , rcu@vger.kernel.org, linux-mm@kvack.org, lkmm@lists.linux.dev References: <20241002010205.1341915-1-mathieu.desnoyers@efficios.com> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 87DED1A0008 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ppyfzbjd9yppkfxadfxj9wtwep6uo1s5 X-HE-Tag: 1727882910-501658 X-HE-Meta: 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 00rKm6mw 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 ;-) 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 >> Cc: Nicholas Piggin >> Cc: Michael Ellerman >> Cc: Greg Kroah-Hartman >> Cc: Sebastian Andrzej Siewior >> Cc: "Paul E. McKenney" >> Cc: Will Deacon >> Cc: Boqun Feng >> Cc: Alan Stern >> Cc: John Stultz >> Cc: Neeraj Upadhyay >> Cc: Boqun Feng >> Cc: Frederic Weisbecker >> Cc: Joel Fernandes >> Cc: Josh Triplett >> Cc: Uladzislau Rezki >> Cc: Steven Rostedt >> Cc: Lai Jiangshan >> Cc: Zqiang >> Cc: Ingo Molnar >> Cc: Waiman Long >> Cc: Mark Rutland >> Cc: Thomas Gleixner >> Cc: Vlastimil Babka >> Cc: maged.michael@gmail.com >> Cc: Mateusz Guzik >> Cc: Jonas Oberhauser >> Cc: rcu@vger.kernel.org >> Cc: linux-mm@kvack.org >> Cc: lkmm@lists.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