Re: [RFC PATCH 0/4] sched+mm: Track lazy active mm existence with hazard pointers
From: Mathieu Desnoyers
Date: Wed Oct 02 2024 - 11:38:19 EST
On 2024-10-02 17:33, Matthew Wilcox wrote:
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?
2 sockets, 96-core per socket:
CPU(s): 384
On-line CPU(s) list: 0-383
Vendor ID: AuthenticAMD
Model name: AMD EPYC 9654 96-Core Processor
CPU family: 25
Model: 17
Thread(s) per core: 2
Core(s) per socket: 96
Socket(s): 2
Stepping: 1
Frequency boost: enabled
CPU(s) scaling MHz: 68%
CPU max MHz: 3709.0000
CPU min MHz: 400.0000
BogoMIPS: 4800.00
Note that Jens Axboe got even more impressive speedups testing this
on his 512-hw-thread EPYC [1] (390% speedup for 192 threads). I've
noticed I had schedstats and sched debug enabled in my config, so I'll
have to re-run my tests.
Thanks,
Mathieu
[1] https://discuss.systems/@axboe@xxxxxxxxxxxxx/113238297041686326
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@xxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: John Stultz <jstultz@xxxxxxxxxx>
Cc: Neeraj Upadhyay <Neeraj.Upadhyay@xxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Uladzislau Rezki <urezki@xxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Cc: Zqiang <qiang.zhang1211@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: maged.michael@xxxxxxxxx
Cc: Mateusz Guzik <mjguzik@xxxxxxxxx>
Cc: Jonas Oberhauser <jonas.oberhauser@xxxxxxxxxxxxxxx>
Cc: rcu@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: lkmm@xxxxxxxxxxxxxxx
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
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com