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From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Sunil Pandey <skpgkp2@gmail.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>,
	 Libc-stable Mailing List <libc-stable@sourceware.org>,
	"H.J. Lu" <hjl.tools@gmail.com>,
	 Florian Weimer <fweimer@redhat.com>,
	Andreas Schwab <schwab@linux-m68k.org>,
	 GNU C Library <libc-alpha@sourceware.org>,
	"Paul A . Clarke" <pc@us.ibm.com>
Subject: Re: [PATCH v6 1/4] Add LLL_MUTEX_READ_LOCK [BZ #28537]
Date: Wed, 28 Sep 2022 20:10:37 -0400	[thread overview]
Message-ID: <CAFUsyfLKcgh7kVW4-cBSm_zYEwqL3ZSDFaAuSRsweuX1w72dcQ@mail.gmail.com> (raw)
In-Reply-To: <CAMAf5_fsUuYbUdiD2KmAV-4RH6QV=k8swJzkOL02awZXbO1NDg@mail.gmail.com>

On Sun, Sep 11, 2022 at 4:19 PM Sunil Pandey <skpgkp2@gmail.com> wrote:
>
> On Wed, Nov 17, 2021 at 5:17 PM Arjan van de Ven via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
> >
> > On 11/17/2021 4:31 PM, H.J. Lu wrote:
> > >> Yes, but the loop will be able to run `max_cnt` iterations much faster now.
> > >> Just wondering if the value needs to be re-tuned. Not that is necessarily needs
> > >> to be.
> > > Maybe if we can find some data to show for.
> > >
> >
> > wondering when this was last tuned.. I assume todays CPUs and CPUs from, say, 5 or 10 years ago
> > have an order of magnitude different performance in this regard....
> > if there wasn't a need to retune during that, maybe this value is so robust that it doesn't need
> > retuning.
> >
> > or maybe it's time to retune this in general sometime soon after this patch goes in ;)
>
> I would like to backport this patch to release branch 2.33 and 2.34

Fine by  me.
>
> Any comments/suggestions or objections on this.
>
> commit d672a98a1af106bd68deb15576710cd61363f7a6
> Author: H.J. Lu <hjl.tools@gmail.com>
> Date:   Tue Nov 2 18:33:07 2021 -0700
>
>     Add LLL_MUTEX_READ_LOCK [BZ #28537]
>
>     CAS instruction is expensive.  From the x86 CPU's point of view, getting
>     a cache line for writing is more expensive than reading.  See Appendix
>     A.2 Spinlock in:
>
>     https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/xeon-lock-scaling-analysis-paper.pdf

      reply	other threads:[~2022-09-29  0:10 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20211111162428.2286605-1-hjl.tools@gmail.com>
     [not found] ` <20211111162428.2286605-5-hjl.tools@gmail.com>
     [not found]   ` <87v90xryvi.fsf@igel.home>
2022-09-11 20:12     ` [PATCH v6 4/4] Avoid extra load with CAS in __pthread_mutex_clocklock_common " Sunil Pandey
2022-09-11 20:15       ` Arjan van de Ven
2022-09-11 21:26         ` Florian Weimer
2022-09-29  0:09       ` Noah Goldstein
     [not found] ` <20211111162428.2286605-3-hjl.tools@gmail.com>
     [not found]   ` <87zgq9rywl.fsf@igel.home>
2022-09-11 20:16     ` [PATCH v6 2/4] Avoid extra load with CAS in __pthread_mutex_lock_full " Sunil Pandey
2022-09-29  0:10       ` Noah Goldstein
     [not found] ` <20211111162428.2286605-2-hjl.tools@gmail.com>
     [not found]   ` <CAFUsyfJH45MshHkFjohENvhJzt1bC=PrUH_3xRn1KubGy9X1HA@mail.gmail.com>
     [not found]     ` <CAMe9rOqOv3WC9rWwtFyzc7rJFDDbNTAfTio-FZC4oW5y751FWA@mail.gmail.com>
     [not found]       ` <CAFUsyf+Yf=QM-0Zj31=k6fANCdXa6XnzVn=Kj6im3xDYbanbnA@mail.gmail.com>
     [not found]         ` <CAMe9rOpE1+1zqtA4xqJNy-RK03jXNzv-JnYSJFtGmtqSa2QqQQ@mail.gmail.com>
     [not found]           ` <924a80cd-202c-99e9-a2d9-1aeda2235b83@linux.intel.com>
2022-09-11 20:19             ` [PATCH v6 1/4] Add LLL_MUTEX_READ_LOCK " Sunil Pandey
2022-09-29  0:10               ` Noah Goldstein [this message]

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