From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>, qianjun.kernel@gmail.com
Cc: will@kernel.org, luto@kernel.org, linux-kernel@vger.kernel.org,
laoar.shao@gmail.com, qais.yousef@arm.com, urezki@gmail.com,
Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH V7 4/4] softirq: Allow early break the softirq processing loop
Date: Mon, 28 Sep 2020 12:09:27 +0200 [thread overview]
Message-ID: <87k0wekyaw.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200928092249.GC2628@hirez.programming.kicks-ass.net>
On Mon, Sep 28 2020 at 11:22, Peter Zijlstra wrote:
> On Tue, Sep 15, 2020 at 07:56:09PM +0800, qianjun.kernel@gmail.com wrote:
>> +/*
>> + * The pending_next_bit is recorded for the next processing order when
>> + * the loop is broken. This per cpu variable is to solve the following
>> + * scenarios:
>
> This, that adds all that complexity, and I think it's wrong. The
> softirqs are priority ordered. Running then again from 0 up if/when you
> break seems 'right'.
No. If you break the loop and then restart from 0 you can starve the
higher numbered ones if the next loop terminates on early because one of
the lower one takes too long. Made that happen with networking :)
See the variant I proposed :)
Thanks,
tglx
prev parent reply other threads:[~2020-09-28 10:09 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 11:56 [PATCH V7 0/4] Softirq:avoid large sched delay from the pending softirqs qianjun.kernel
2020-09-15 11:56 ` [PATCH V7 1/4] softirq: Use sched_clock() based timeout qianjun.kernel
2020-09-24 8:34 ` Thomas Gleixner
2020-09-15 11:56 ` [PATCH V7 2/4] softirq: Factor loop termination condition qianjun.kernel
2020-09-24 8:36 ` Thomas Gleixner
2020-09-24 12:31 ` Thomas Gleixner
2020-09-15 11:56 ` [PATCH V7 3/4] softirq: Rewrite softirq processing loop qianjun.kernel
2020-09-15 11:56 ` [PATCH V7 4/4] softirq: Allow early break the " qianjun.kernel
2020-09-24 15:37 ` Thomas Gleixner
2020-09-24 23:08 ` Frederic Weisbecker
2020-09-24 23:10 ` Frederic Weisbecker
2020-09-25 22:37 ` Thomas Gleixner
2020-09-25 0:42 ` Frederic Weisbecker
2020-09-25 22:42 ` Thomas Gleixner
2020-09-26 12:22 ` Frederic Weisbecker
2020-09-28 10:51 ` jun qian
2020-09-29 11:44 ` Frederic Weisbecker
2020-10-09 15:01 ` Qais Yousef
2020-10-13 10:43 ` Frederic Weisbecker
2020-10-13 12:40 ` Qais Yousef
2020-09-26 2:00 ` jun qian
2020-09-27 1:05 ` [softirq] 56c21abbe6: will-it-scale.per_process_ops -9.1% regression kernel test robot
2020-09-28 9:20 ` [PATCH V7 4/4] softirq: Allow early break the softirq processing loop Peter Zijlstra
2020-09-28 11:15 ` jun qian
2020-09-28 9:22 ` Peter Zijlstra
2020-09-28 10:09 ` Thomas Gleixner [this message]
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