From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: linux-kernel@vger.kernel.org, lizefan@huawei.com,
mingo@kernel.org, tglx@linutronix.de, josh@joshtriplett.org,
yury.norov@gmail.com, peterz@infradead.org, paulmck@kernel.org,
fweisbec@gmail.com, linux@rasmusvillemoes.dk
Subject: Re: [PATCH 6/8] lib: bitmap: support "N" as an alias for size of bitmap
Date: Tue, 26 Jan 2021 23:37:30 +0200 [thread overview]
Message-ID: <YBCLmrCSwBRkTAhT@smile.fi.intel.com> (raw)
In-Reply-To: <20210126171141.122639-7-paul.gortmaker@windriver.com>
On Tue, Jan 26, 2021 at 12:11:39PM -0500, Paul Gortmaker wrote:
> While this is done for all bitmaps, the original use case in mind was
> for CPU masks and cpulist_parse() as described below.
>
> It seems that a common configuration is to use the 1st couple cores for
> housekeeping tasks. This tends to leave the remaining ones to form a
> pool of similarly configured cores to take on the real workload of
> interest to the user.
>
> So on machine A - with 32 cores, it could be 0-3 for "system" and then
> 4-31 being used in boot args like nohz_full=, or rcu_nocbs= as part of
> setting up the worker pool of CPUs.
>
> But then newer machine B is added, and it has 48 cores, and so while
> the 0-3 part remains unchanged, the pool setup cpu list becomes 4-47.
>
> Multiple deployment becomes easier when we can just simply replace 31
> and 47 with "N" and let the system substitute in the actual number at
> boot; a number that it knows better than we do.
I would accept lower 'n' as well.
...
> -static const char *bitmap_getnum(const char *str, unsigned int *num)
> +static const char *__bitmap_getnum(const char *str, unsigned int nbits,
> + unsigned int *num)
> {
> unsigned long long n;
> unsigned int len;
>
> + if (str[0] == 'N') {
> + *num = nbits - 1;
> + return str + 1;
> + }
But locating it here makes possible to enter a priori invalid input, like N for
start of the region.
I think this should be separate helper which is called in places where it makes
sense.
> len = _parse_integer(str, 10, &n);
> if (!len)
> return ERR_PTR(-EINVAL);
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2021-01-27 3:35 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 17:11 [PATCH v3 0/8] support for bitmap (and hence CPU) list "N" abbreviation Paul Gortmaker
2021-01-26 17:11 ` [PATCH 1/8] lib: test_bitmap: clearly separate ERANGE from EINVAL tests Paul Gortmaker
2021-01-26 21:04 ` Andy Shevchenko
2021-01-27 7:21 ` Paul Gortmaker
2021-01-26 17:11 ` [PATCH 2/8] lib: test_bitmap: add more start-end:offset/len tests Paul Gortmaker
2021-01-26 21:11 ` Andy Shevchenko
2021-01-27 3:03 ` Yury Norov
2021-01-26 17:11 ` [PATCH 3/8] lib: bitmap: fold nbits into region struct Paul Gortmaker
2021-01-26 21:16 ` Andy Shevchenko
2021-01-26 21:18 ` Andy Shevchenko
2021-01-27 8:02 ` Paul Gortmaker
2021-01-28 0:47 ` Yury Norov
2021-01-28 10:17 ` Andy Shevchenko
2021-01-27 3:08 ` Yury Norov
2021-01-26 17:11 ` [PATCH 4/8] lib: bitmap: move ERANGE check from set_region to check_region Paul Gortmaker
2021-01-26 21:19 ` Andy Shevchenko
2021-01-27 3:12 ` Yury Norov
2021-01-26 17:11 ` [PATCH 5/8] lib: bitmap_getnum: separate arg into region and field Paul Gortmaker
2021-01-26 21:23 ` Andy Shevchenko
2021-01-27 2:58 ` Yury Norov
2021-01-27 8:38 ` Paul Gortmaker
2021-01-26 17:11 ` [PATCH 6/8] lib: bitmap: support "N" as an alias for size of bitmap Paul Gortmaker
2021-01-26 21:37 ` Andy Shevchenko [this message]
2021-01-26 21:41 ` Andy Shevchenko
2021-01-27 17:57 ` Yury Norov
2021-01-27 8:20 ` Paul Gortmaker
2021-01-26 17:11 ` [PATCH 7/8] lib: test_bitmap: add tests for "N" alias Paul Gortmaker
2021-01-26 17:11 ` [PATCH 8/8] rcu: deprecate "all" option to rcu_nocbs= Paul Gortmaker
2021-01-26 21:36 ` Yury Norov
2021-01-26 22:17 ` Paul E. McKenney
2021-01-26 22:27 ` [PATCH v3 0/8] support for bitmap (and hence CPU) list "N" abbreviation Yury Norov
2021-01-27 9:12 ` Paul Gortmaker
2021-02-09 22:58 [PATCH v4 " Paul Gortmaker
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
2021-02-21 8:08 [PATCH v5 0/8] support for bitmap (and hence CPU) list "N" abbreviation Paul Gortmaker
2021-02-21 8:08 ` [PATCH 6/8] lib: bitmap: support "N" as an alias for size of bitmap Paul Gortmaker
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YBCLmrCSwBRkTAhT@smile.fi.intel.com \
--to=andriy.shevchenko@linux.intel.com \
--cc=fweisbec@gmail.com \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@rasmusvillemoes.dk \
--cc=lizefan@huawei.com \
--cc=mingo@kernel.org \
--cc=paul.gortmaker@windriver.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=yury.norov@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).