From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, lkmm@lists.linux.dev
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Will Deacon <will@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
Waiman Long <longman@redhat.com>,
Davidlohr Bueso <dave@stgolabs.net>,
"Paul E. McKenney" <paulmck@kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
Frederic Weisbecker <frederic@kernel.org>,
Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
Joel Fernandes <joelagnelf@nvidia.com>,
Uladzislau Rezki <urezki@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Zqiang <qiang.zhang@linux.dev>, Breno Leitao <leitao@debian.org>,
aeh@meta.com, netdev@vger.kernel.org, edumazet@google.com,
jhs@mojatatu.com, kernel-team@meta.com,
Erik Lundgren <elundgren@meta.com>
Subject: [PATCH 0/8] Introduce simple hazard pointers for lockdep
Date: Tue, 24 Jun 2025 20:10:53 -0700 [thread overview]
Message-ID: <20250625031101.12555-1-boqun.feng@gmail.com> (raw)
Hi,
This is the official first version of simple hazard pointers following
the RFC:
https://lore.kernel.org/lkml/20250414060055.341516-1-boqun.feng@gmail.com/
I rebase it onto v6.16-rc3 and hope to get more feedback this time.
Thanks a lot for Breno Leitao to try the RFC out and share the numbers.
I did an extra comparison this time, between the shazptr solution and
the synchronize_rcu_expedited() solution. In my test, during a 100 times
"tc qdisc replace" run:
* IPI rate with the shazptr solution: ~14 per second per core.
* IPI rate with synchronize_rcu_expedited(): ~140 per second per core.
(IPI results were from the 'CAL' line in /proc/interrupt)
This shows that while both solutions have the similar speedup, shazptr
solution avoids the introduce of high IPI rate compared to
synchronize_rcu_expedited().
Feedback is welcome and please let know if there is any concern or
suggestion. Thanks!
Regards,
Boqun
--------------------------------------
Please find the old performance below:
On my system (a 96-cpu VMs), the results of:
time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1: mq
are (with lockdep enabled):
(without the patchset)
real 0m1.039s
user 0m0.001s
sys 0m0.069s
(with the patchset)
real 0m0.053s
user 0m0.000s
sys 0m0.051s
i.e. almost 20x speed-up.
Other comparisons between RCU and shazptr, the rcuscale results (using
default configuration from
tools/testing/selftests/rcutorture/bin/kvm.sh):
RCU:
Average grace-period duration: 7470.02 microseconds
Minimum grace-period duration: 3981.6
50th percentile grace-period duration: 6002.73
90th percentile grace-period duration: 7008.93
99th percentile grace-period duration: 10015
Maximum grace-period duration: 142228
shazptr:
Average grace-period duration: 0.845825 microseconds
Minimum grace-period duration: 0.199
50th percentile grace-period duration: 0.585
90th percentile grace-period duration: 1.656
99th percentile grace-period duration: 3.872
Maximum grace-period duration: 3049.05
shazptr (skip_synchronize_self_scan=1, i.e. always let scan kthread to
wakeup):
Average grace-period duration: 467.861 microseconds
Minimum grace-period duration: 92.913
50th percentile grace-period duration: 440.691
90th percentile grace-period duration: 460.623
99th percentile grace-period duration: 650.068
Maximum grace-period duration: 5775.46
shazptr_wildcard (i.e. readers always use SHAZPTR_WILDCARD):
Average grace-period duration: 599.569 microseconds
Minimum grace-period duration: 1.432
50th percentile grace-period duration: 582.631
90th percentile grace-period duration: 781.704
99th percentile grace-period duration: 1160.26
Maximum grace-period duration: 6727.53
shazptr_wildcard (skip_synchronize_self_scan=1):
Average grace-period duration: 460.466 microseconds
Minimum grace-period duration: 303.546
50th percentile grace-period duration: 424.334
90th percentile grace-period duration: 482.637
99th percentile grace-period duration: 600.214
Maximum grace-period duration: 4126.94
Boqun Feng (8):
Introduce simple hazard pointers
shazptr: Add refscale test
shazptr: Add refscale test for wildcard
shazptr: Avoid synchronize_shaptr() busy waiting
shazptr: Allow skip self scan in synchronize_shaptr()
rcuscale: Allow rcu_scale_ops::get_gp_seq to be NULL
rcuscale: Add tests for simple hazard pointers
locking/lockdep: Use shazptr to protect the key hashlist
include/linux/shazptr.h | 73 +++++++++
kernel/locking/Makefile | 2 +-
kernel/locking/lockdep.c | 11 +-
kernel/locking/shazptr.c | 318 +++++++++++++++++++++++++++++++++++++++
kernel/rcu/rcuscale.c | 60 +++++++-
kernel/rcu/refscale.c | 77 ++++++++++
6 files changed, 534 insertions(+), 7 deletions(-)
create mode 100644 include/linux/shazptr.h
create mode 100644 kernel/locking/shazptr.c
--
2.39.5 (Apple Git-154)
next reply other threads:[~2025-06-25 3:11 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-25 3:10 Boqun Feng [this message]
2025-06-25 3:10 ` [PATCH 1/8] Introduce simple hazard pointers Boqun Feng
2025-06-25 10:00 ` Peter Zijlstra
2025-06-25 14:25 ` Mathieu Desnoyers
2025-06-25 15:05 ` Boqun Feng
2025-06-25 15:52 ` Waiman Long
2025-06-25 16:09 ` Boqun Feng
2025-06-25 17:47 ` Waiman Long
2025-06-25 3:10 ` [PATCH 2/8] shazptr: Add refscale test Boqun Feng
2025-06-25 10:02 ` Peter Zijlstra
2025-06-25 3:10 ` [PATCH 3/8] shazptr: Add refscale test for wildcard Boqun Feng
2025-06-25 10:03 ` Peter Zijlstra
2025-06-25 3:10 ` [PATCH 4/8] shazptr: Avoid synchronize_shaptr() busy waiting Boqun Feng
2025-06-25 11:40 ` Peter Zijlstra
2025-06-25 11:56 ` Peter Zijlstra
2025-06-25 13:56 ` Frederic Weisbecker
2025-06-25 15:24 ` Boqun Feng
2025-06-26 13:45 ` Frederic Weisbecker
2025-06-25 3:10 ` [PATCH 5/8] shazptr: Allow skip self scan in synchronize_shaptr() Boqun Feng
2025-06-25 3:10 ` [PATCH 6/8] rcuscale: Allow rcu_scale_ops::get_gp_seq to be NULL Boqun Feng
2025-06-25 3:11 ` [PATCH 7/8] rcuscale: Add tests for simple hazard pointers Boqun Feng
2025-06-25 3:11 ` [PATCH 8/8] locking/lockdep: Use shazptr to protect the key hashlist Boqun Feng
2025-06-25 11:59 ` Peter Zijlstra
2025-06-25 14:18 ` Boqun Feng
2025-07-10 14:06 ` Breno Leitao
2025-07-11 2:31 ` Boqun Feng
2025-06-25 12:05 ` [PATCH 0/8] Introduce simple hazard pointers for lockdep Christoph Hellwig
2025-06-25 14:08 ` Boqun Feng
2025-06-26 10:16 ` Christoph Hellwig
2025-06-26 13:45 ` Mathieu Desnoyers
2025-06-26 15:47 ` Boqun Feng
2025-06-27 2:56 ` Paul E. McKenney
2025-06-25 12:25 ` Mathieu Desnoyers
2025-06-25 13:21 ` Boqun Feng
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20250625031101.12555-1-boqun.feng@gmail.com \
--to=boqun.feng@gmail.com \
--cc=aeh@meta.com \
--cc=dave@stgolabs.net \
--cc=edumazet@google.com \
--cc=elundgren@meta.com \
--cc=frederic@kernel.org \
--cc=jhs@mojatatu.com \
--cc=jiangshanlai@gmail.com \
--cc=joelagnelf@nvidia.com \
--cc=josh@joshtriplett.org \
--cc=kernel-team@meta.com \
--cc=leitao@debian.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lkmm@lists.linux.dev \
--cc=longman@redhat.com \
--cc=mathieu.desnoyers@efficios.com \
--cc=mingo@kernel.org \
--cc=neeraj.upadhyay@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=qiang.zhang@linux.dev \
--cc=rcu@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=urezki@gmail.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).