linux-kernel - Re: [PATCH-tip v2 06/12] locking/rwsem: Wake up almost all readers in wait queue

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Message-ID: <f5facb9a-59ce-d59e-9e7d-4c167cf0ca32@redhat.com>
Date:   Wed, 10 Apr 2019 13:53:06 -0400
From:   Waiman Long <longman@...hat.com>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [PATCH-tip v2 06/12] locking/rwsem: Wake up almost all readers in
 wait queue

On 04/10/2019 01:22 PM, Davidlohr Bueso wrote:
> On Wed, 10 Apr 2019, Waiman Long wrote:
>> There are 2 major reasons why there is a limit.
>>
>> 1) It will be unfair to the task that needs to spend so much of its own
>> CPU time to wake up too many readers.
>
> This has never been a problem before.
>

In real workloads, you seldom have more than a couple dozens of readers
waiting in the queue.

Cheers,
Longman