From: Linus Torvalds <torvalds@linux-foundation.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ankur Arora <ankur.a.arora@oracle.com>,
linux-mm@kvack.org, x86@kernel.org, akpm@linux-foundation.org,
luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com,
hpa@zytor.com, mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, willy@infradead.org,
mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com,
raghavendra.kt@amd.com, boris.ostrovsky@oracle.com,
konrad.wilk@oracle.com, jgross@suse.com,
andrew.cooper3@citrix.com,
Joel Fernandes <joel@joelfernandes.org>,
Youssef Esmat <youssefesmat@chromium.org>,
Vineeth Pillai <vineethrp@google.com>,
Suleiman Souhlal <suleiman@google.com>,
Ingo Molnar <mingo@kernel.org>,
Daniel Bristot de Oliveira <bristot@kernel.org>
Subject: Re: [POC][RFC][PATCH v2] sched: Extended Scheduler Time Slice
Date: Thu, 26 Oct 2023 08:50:32 -1000 [thread overview]
Message-ID: <CAHk-=whnyt2TccpDaWGTbDsVkKApL3c2FtDPMEwuTmeu_cEL8Q@mail.gmail.com> (raw)
In-Reply-To: <f5b0fffa-423a-4571-be6c-383399274328@efficios.com>
On Thu, 26 Oct 2023 at 08:36, Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> > asm volatile("xchg %b0,%1"
>
> which has an implicit lock prefix (xchg with a memory operand is a
> special-case):
Yeah, this is why we do "percpu_xchg()" - which does not want locked
semantics - as a "cmpxchg" loop.
Steven, check out
arch/x86/include/asm/percpu.h
for a rough implementation of a 'xchg()' without SMP coherency, just
cpu-local one (ie atomic wrt being preempted by the kernel, but not
atomic wrt other CPU's accessing the same variable concurrently)
Linus
next prev parent reply other threads:[~2023-10-26 18:50 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-26 3:54 Steven Rostedt
2023-10-26 10:59 ` Peter Zijlstra
2023-10-26 11:14 ` Steven Rostedt
2023-10-26 18:36 ` Mathieu Desnoyers
2023-10-26 18:50 ` Linus Torvalds [this message]
2023-10-26 18:59 ` Mathieu Desnoyers
2023-10-26 19:36 ` Steven Rostedt
2023-10-26 20:45 ` Steven Rostedt
[not found] ` <644da047-2f7a-4d55-a339-f2dc28d2c852@efficios.com>
[not found] ` <20231027122442.5c76dd62@gandalf.local.home>
2023-10-27 16:35 ` Mathieu Desnoyers
2023-10-27 16:49 ` Steven Rostedt
2023-10-30 12:56 ` Mathieu Desnoyers
2023-10-30 13:45 ` Steven Rostedt
2023-10-30 18:05 ` Mathieu Desnoyers
2023-10-30 18:19 ` Steven Rostedt
2023-10-30 18:27 ` Mathieu Desnoyers
2023-10-30 18:39 ` Steven Rostedt
2023-10-26 19:20 ` Steven Rostedt
2023-10-26 21:35 ` Steven Rostedt
2023-10-27 21:52 ` Steven Rostedt
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