From: Peter Oskolkov <posk@google.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Paul Turner <pjt@google.com>, Ben Segall <bsegall@google.com>,
Peter Oskolkov <posk@posk.io>,
Joel Fernandes <joel@joelfernandes.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrei Vagin <avagin@google.com>,
Jim Newsome <jnewsome@torproject.org>
Subject: Re: [RFC PATCH v0.1 4/9] sched/umcg: implement core UMCG API
Date: Fri, 21 May 2021 15:01:24 -0700 [thread overview]
Message-ID: <CAPNVh5foSzWj3XHoONjvzmLLXOi9u3ojNmdfegohpufx1YYXgg@mail.gmail.com> (raw)
In-Reply-To: <CALCETrXo=5r+i6f3qvSp4mEHcR93U3F0S0kFr8d5JGU6WetSqw@mail.gmail.com>
On Fri, May 21, 2021 at 12:32 PM Andy Lutomirski <luto@kernel.org> wrote:
>
> On Thu, May 20, 2021 at 11:36 AM Peter Oskolkov <posk@google.com> wrote:
> >
> > Implement version 1 of core UMCG API (wait/wake/swap).
> >
> > As has been outlined in
> > https://lore.kernel.org/lkml/20200722234538.166697-1-posk@posk.io/,
> > efficient and synchronous on-CPU context switching is key
> > to enabling two broad use cases: in-process M:N userspace scheduling
> > and fast X-process RPCs for security wrappers.
> >
> > High-level design considerations/approaches used:
> > - wait & wake can race with each other;
> > - offload as much work as possible to libumcg in tools/lib/umcg,
> > specifically:
> > - most state changes, e.g. RUNNABLE <=> RUNNING, are done in
> > the userspace (libumcg);
> > - retries are offloaded to the userspace.
>
> Do you have some perf numbers as to how long a UMCG context switch
> takes compared to a normal one?
I'm not sure what is a "normal context switch" in this context. Futex
wakeup on a remote idle CPU takes 5-10usec; an on-CPU UMCG context
switch takes less than 1usec; futex wake + futex wait on the same CPU
(taskset ***) takes about 1-1.5usec in my benchmarks.
>
> --Andy
next prev parent reply other threads:[~2021-05-21 22:01 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-20 18:36 [RFC PATCH v0.1 0/9] UMCG early preview/RFC patchset Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 1/9] sched/umcg: add UMCG syscall stubs and CONFIG_UMCG Peter Oskolkov
2021-05-22 18:40 ` kernel test robot
2021-05-22 21:49 ` kernel test robot
2021-05-20 18:36 ` [RFC PATCH v0.1 2/9] sched/umcg: add uapi/linux/umcg.h and sched/umcg.c Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 3/9] sched: add WF_CURRENT_CPU and externise ttwu Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 4/9] sched/umcg: implement core UMCG API Peter Oskolkov
2021-05-21 19:06 ` Andrei Vagin
2021-05-21 21:31 ` Jann Horn
2021-05-21 22:03 ` Peter Oskolkov
2021-05-21 19:32 ` Andy Lutomirski
2021-05-21 22:01 ` Peter Oskolkov [this message]
2021-05-21 21:33 ` Jann Horn
2021-06-09 13:01 ` Peter Zijlstra
2021-05-20 18:36 ` [RFC PATCH v0.1 5/9] lib/umcg: implement UMCG core API for userspace Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 6/9] selftests/umcg: add UMCG core API selftest Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 7/9] sched/umcg: add UMCG server/worker API (early RFC) Peter Oskolkov
2021-05-21 20:17 ` Andrei Vagin
2021-05-22 18:29 ` kernel test robot
2021-05-22 19:34 ` kernel test robot
2021-05-22 20:19 ` kernel test robot
2021-05-20 18:36 ` [RFC PATCH v0.1 8/9] lib/umcg: " Peter Oskolkov
2021-05-20 18:36 ` [RFC PATCH v0.1 9/9] selftests/umcg: add UMCG server/worker API selftest Peter Oskolkov
2021-05-20 21:17 ` [RFC PATCH v0.1 0/9] UMCG early preview/RFC patchset Jonathan Corbet
2021-05-20 21:38 ` Peter Oskolkov
2021-05-21 0:15 ` Randy Dunlap
2021-05-21 8:04 ` Peter Zijlstra
2021-05-21 15:08 ` Jonathan Corbet
2021-05-21 16:03 ` Peter Oskolkov
2021-05-21 19:17 ` Jonathan Corbet
2021-05-27 0:06 ` Peter Oskolkov
2021-05-27 15:41 ` Jonathan Corbet
[not found] ` <CAEWA0a72SvpcuN4ov=98T3uWtExPCr7BQePOgjkqD1ofWKEASw@mail.gmail.com>
2021-05-21 19:13 ` Peter Oskolkov
2021-05-21 23:08 ` Jann Horn
2021-06-09 12:54 ` Peter Zijlstra
2021-06-09 20:18 ` Peter Oskolkov
2021-06-10 18:02 ` Peter Zijlstra
2021-06-10 20:06 ` Peter Oskolkov
2021-07-07 17:45 ` Thierry Delisle
2021-07-08 21:44 ` Peter Oskolkov
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