From: Paul Gortmaker <paul.gortmaker@windriver.com> To: Andy Shevchenko <andriy.shevchenko@linux.intel.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: Wed, 27 Jan 2021 03:20:47 -0500 [thread overview] Message-ID: <20210127082046.GF23530@windriver.com> (raw) In-Reply-To: <YBCLmrCSwBRkTAhT@smile.fi.intel.com> [Re: [PATCH 6/8] lib: bitmap: support "N" as an alias for size of bitmap] On 26/01/2021 (Tue 23:37) Andy Shevchenko wrote: > 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. Actually, no. N can be valid input for start of the region - or for any field in the region. I was originally thinking like you -- that N was only valid as the end of the region, but Yury made a compelling argument that N should be treated exactly as any other number is. Skip down to where Yury says: So, when I do echo N-N > cpuset.cpus, I want it to work as if I do echo 15-15 > cpuset.cpus. https://lore.kernel.org/lkml/20210126171811.GC23530@windriver.com/ You weren't Cc'd at that point as I'd not added any self-test changes to the series yet - so you didn't probably see that discussion. This is why you'll see "N-N:N/N" added as a self-test that works. It doesn't make any more sense than using 15-15:15/15 does (vs. "15") but both are equally valid inputs, in that they don't trigger an error. Thanks, Paul. -- > > 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 8:24 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 2021-01-26 21:41 ` Andy Shevchenko 2021-01-27 17:57 ` Yury Norov 2021-01-27 8:20 ` Paul Gortmaker [this message] 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=20210127082046.GF23530@windriver.com \ --to=paul.gortmaker@windriver.com \ --cc=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=paulmck@kernel.org \ --cc=peterz@infradead.org \ --cc=tglx@linutronix.de \ --cc=yury.norov@gmail.com \ --subject='Re: [PATCH 6/8] lib: bitmap: support "N" as an alias for size of bitmap' \ /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
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).