From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: paulmck@kernel.org, Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>,
linux-kernel@vger.kernel.org, Li Zefan <lizefan@huawei.com>,
Ingo Molnar <mingo@kernel.org>, Yury Norov <yury.norov@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Josh Triplett <josh@joshtriplett.org>,
Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH v4 0/8] support for bitmap (and hence CPU) list "N" abbreviation
Date: Thu, 11 Feb 2021 12:04:51 +0100 [thread overview]
Message-ID: <da9ca86e-4113-f0ad-6120-3b3cbea5c836@rasmusvillemoes.dk> (raw)
In-Reply-To: <20210210175751.GH2743@paulmck-ThinkPad-P72>
On 10/02/2021 18.57, Paul E. McKenney wrote:
> On Wed, Feb 10, 2021 at 06:26:54PM +0200, Andy Shevchenko wrote:
>> On Tue, Feb 09, 2021 at 05:58:59PM -0500, Paul Gortmaker wrote:
>>> The basic objective here was to add support for "nohz_full=8-N" and/or
>>> "rcu_nocbs="4-N" -- essentially introduce "N" as a portable reference
>>> to the last core, evaluated at boot for anything using a CPU list.
>>
>> I thought we kinda agreed that N is confusing and L is better.
>> N to me is equal to 32 on 32 core system as *number of cores / CPUs*. While L
>> sounds better as *last available CPU number*.
>
> The advantage of "N" is that people will automatically recognize it as
> "last thing" or number of things" because "N" has long been used in
> both senses. In contrast, someone seeing "0-L" for the first time is
> likely to go "What???".
Completely agree. The patch that introduces this even updates
Documentation/ at the same time, and if people are confused just because
they don't RTFM, xkcd#293 applies. So let's please just paint the
bikeshed N. (As for case insensitivity, I don't see the point, it just
makes documentation and implementation more cumbersome and confusing.
Just document and implement _one_ way of doing this.)
As for a future syntax for "last 4 cpus", it's common to accept a
negative index to mean count from the end, so unless we already accept
-4 as a shorthand for 0-4 (haven't checked), that could be -4-N. But
regardless, I also agree with Paul on this point, that's for a future
time when the need arises.
Rasmus
prev parent reply other threads:[~2021-02-11 11:36 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 22:58 [PATCH v4 0/8] support for bitmap (and hence CPU) list "N" abbreviation Paul Gortmaker
2021-02-09 22:59 ` [PATCH 1/8] lib: test_bitmap: clearly separate ERANGE from EINVAL tests Paul Gortmaker
2021-02-09 22:59 ` [PATCH 2/8] lib: test_bitmap: add tests to trigger ERANGE case Paul Gortmaker
2021-02-10 16:27 ` Andy Shevchenko
2021-02-09 22:59 ` [PATCH 3/8] lib: test_bitmap: add more start-end:offset/len tests Paul Gortmaker
2021-02-09 22:59 ` [PATCH 4/8] lib: bitmap: move ERANGE check from set_region to check_region Paul Gortmaker
2021-02-10 16:28 ` Andy Shevchenko
2021-02-09 22:59 ` [PATCH 5/8] lib: bitmap: pair nbits value with region struct Paul Gortmaker
2021-02-10 16:34 ` Andy Shevchenko
2021-02-09 22:59 ` [PATCH 6/8] lib: bitmap: support "N" as an alias for size of bitmap Paul Gortmaker
2021-02-09 23:16 ` Yury Norov
2021-02-10 15:58 ` Paul Gortmaker
2021-02-10 16:49 ` Andy Shevchenko
2021-02-12 1:24 ` Yury Norov
2021-02-21 8:07 ` Paul Gortmaker
2021-02-09 22:59 ` [PATCH 7/8] lib: test_bitmap: add tests for "N" alias Paul Gortmaker
2021-02-09 22:59 ` [PATCH 8/8] rcu: deprecate "all" option to rcu_nocbs= Paul Gortmaker
2021-02-10 16:26 ` [PATCH v4 0/8] support for bitmap (and hence CPU) list "N" abbreviation Andy Shevchenko
2021-02-10 17:57 ` Paul E. McKenney
2021-02-10 23:50 ` Yury Norov
2021-02-11 0:23 ` Paul E. McKenney
2021-02-12 0:23 ` Yury Norov
2021-02-12 0:38 ` Paul E. McKenney
2021-02-21 8:02 ` Paul Gortmaker
2021-02-11 11:04 ` Rasmus Villemoes [this message]
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