From: Tejun Heo <tj@kernel.org>
To: Josh Don <joshdon@google.com>
Cc: paulmck@kernel.org, Hao Luo <haoluo@google.com>,
davemarchevsky@meta.com, David Vernet <dvernet@meta.com>,
Neel Natu <neelnatu@google.com>,
Jack Humphries <jhumphri@google.com>,
bpf@vger.kernel.org, ast@kernel.org
Subject: Re: BPF memory model
Date: Fri, 8 Sep 2023 12:07:29 -1000 [thread overview]
Message-ID: <ZPubIZLXFuAsfN7a@slm.duckdns.org> (raw)
In-Reply-To: <CABk29Nva+c6oBZra6srWGcfxMEquOP30dReM-PgW_Wh+zKiBuQ@mail.gmail.com>
Hello,
On Fri, Sep 08, 2023 at 01:26:11PM -0700, Josh Don wrote:
> I'm writing BPF programs for scheduling (ie. sched_ext), so these are
> getting invoked in hot paths and invoked concurrently across multiple
> cpus (for example, pick_next_task, enqueue_task, etc.). The kernel is
> responsible for relaying ground truth, userspace makes O(ms)
> scheduling decisions, and BPF makes O(us) scheduling decisions.
> BPF-BPF concurrency is possible with spinlocks and RMW, BPF-userspace
> can currently only really use RMW. My line of questioning is more
> forward looking, as I'm preemptively thinking of how to ensure
> kernel-like scheduling performance, since BPF spinlock or RMW is
> sometimes overkill :) I would think that barrier() and smp_mb() would
> probably be the minimum viable set (at least for x86) that people
> would find useful, but maybe others can chime in.
My personal favorite set is store_release/load_acquire(). I have a hard time
thinking up cases which can't be covered by them and they're basically free
on x86.
Thanks.
--
tejun
next prev parent reply other threads:[~2023-09-08 22:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-07 22:00 BPF memory model Josh Don
2023-09-08 8:42 ` Paul E. McKenney
2023-09-08 20:26 ` Josh Don
2023-09-08 22:07 ` Tejun Heo [this message]
2023-09-08 23:16 ` Alexei Starovoitov
2023-09-09 12:47 ` Paul E. McKenney
2023-09-18 15:09 ` Barret Rhoden
2023-09-19 9:52 ` Paul E. McKenney
2023-09-19 15:55 ` Barret Rhoden
2023-10-16 16:48 ` Paul E. McKenney
2023-10-16 17:17 ` Jose E. Marchesi
2023-11-13 18:53 ` Barret Rhoden
2023-11-13 20:03 ` Paul E. McKenney
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