From: Ankur Arora <ankur.a.arora@oracle.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ankur Arora <ankur.a.arora@oracle.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
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] sched: Extended Scheduler Time Slice
Date: Wed, 25 Oct 2023 22:03:48 -0700 [thread overview]
Message-ID: <8734xyf00b.fsf@oracle.com> (raw)
In-Reply-To: <20231025102952.GG37471@noisy.programming.kicks-ass.net>
Peter Zijlstra <peterz@infradead.org> writes:
> On Wed, Oct 25, 2023 at 05:42:19AM -0400, Steven Rostedt wrote:
>
>> So, bit 1 is for user space to tell the kernel "please extend me", and bit
>> two is for the kernel to tell user space "OK, I extended you, but call
>> sched_yield() when done".
>
> So what if it doesn't ? Can we kill it for not playing nice ?
>
> [ aside from it being bit 0 and bit 1 as you yourself point out, it is
> also jarring you use a numeral for one and write out the other. ]
>
> That said, I properly hate all these things, extending a slice doesn't
> reliably work and we're always left with people demanding an ever longer
> extension.
>
> The *much* better heuristic is what the kernel uses, don't spin if the
> lock holder isn't running.
Something like vcpu_is_preempted()? That helps deal with preemption
once it has happened, but an ahead of time signal would be much more
efficient.
And, guest lock holder preemption was a big enough issue that we drop
down to test-and-set spinlocks in some cases.
Thanks
--
ankur
next prev parent reply other threads:[~2023-10-26 5:05 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-25 9:42 [POC][RFC][PATCH] sched: Extended Scheduler Time Slice Steven Rostedt
2023-10-25 9:46 ` Steven Rostedt
2023-10-25 10:29 ` Peter Zijlstra
2023-10-25 12:54 ` Steven Rostedt
2023-10-25 13:55 ` Peter Zijlstra
2023-10-25 14:31 ` Steven Rostedt
2023-10-25 14:53 ` Mathieu Desnoyers
2023-10-25 15:07 ` Steven Rostedt
2023-10-25 15:42 ` Mathieu Desnoyers
2023-10-25 16:24 ` Mateusz Guzik
2023-10-25 17:17 ` Steven Rostedt
2023-10-25 18:49 ` Mathieu Desnoyers
2023-10-25 19:19 ` Steven Rostedt
2023-10-25 21:56 ` Mathieu Desnoyers
2023-10-26 8:54 ` Peter Zijlstra
2023-10-26 13:40 ` Steven Rostedt
2023-10-26 15:49 ` Steven Rostedt
2023-10-26 16:31 ` Daniel Bristot de Oliveira
2023-10-26 17:26 ` Steven Rostedt
2023-10-26 8:44 ` Peter Zijlstra
2023-10-26 13:16 ` Steven Rostedt
2023-10-30 13:29 ` Peter Zijlstra
2023-10-30 13:52 ` Steven Rostedt
2023-10-26 5:03 ` Ankur Arora [this message]
2023-10-25 15:12 ` Steven Rostedt
2023-10-25 15:34 ` Rasmus Villemoes
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