From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751117AbcGQNtu (ORCPT ); Sun, 17 Jul 2016 09:49:50 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:36261 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750866AbcGQNts (ORCPT ); Sun, 17 Jul 2016 09:49:48 -0400 X-IBM-Helo: d03dlp01.boulder.ibm.com X-IBM-MailFrom: xinhui@linux.vnet.ibm.com Subject: Re: [PATCH v3] lib/bitmap.c: enhance bitmap syntax To: Noam Camus , decot@googlers.com References: <1468737234-29232-1-git-send-email-noamca@mellanox.com> <1468743057-29498-1-git-send-email-noamca@mellanox.com> Cc: ben@decadent.org.uk, davem@davemloft.net, akpm@linux-foundation.org, linux-kernel@vger.kernel.org From: Pan Xinhui Date: Sun, 17 Jul 2016 21:50:15 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <1468743057-29498-1-git-send-email-noamca@mellanox.com> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16071713-0020-0000-0000-00000957FBCC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16071713-0021-0000-0000-000053C27742 Message-Id: <3d1f92a0-4c67-54de-11d6-927d88e8de7b@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-07-17_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1607170173 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ÔÚ 16/7/17 16:10, Noam Camus дµÀ: > From: Noam Camus > > Today there are platforms with many CPUs (up to 4K). > Trying to boot only part of the CPUs may result in too long string. > > For example lets take NPS platform that is part of arch/arc. > This platform have SMP system with 256 cores each with > 16 HW threads (SMT machine) where HW thread appears as CPU to the kernel. > In this example there is total of 4K CPUs. > When one tries to boot only part of the HW threads from each core the > string representing the map may be long... > For example if for sake of performance we decided to boot only first half > of HW threads of each core the map will look like: > 0-7,16-23,32-39,...,4080-4087 > > This patch introduce new syntax to accommodate with such use case. > I added an optional postfix to a range of CPUs which will choose > according to given modulo the desired range of reminders i.e.: > %modulo= > > For example, above map can be described in new syntax like this: > 0-4095%16=0-7 > I really think it is better to implement one function to generic a string which contanis the cpus you want to boot on, then pass this string to __bitmap_parselist. > Note that this patch is backward compatible with current syntax. > > Signed-off-by: Noam Camus > --- > Any sugestions for simpler syntax which keeps its generality are welcomed. > > Change Log: > V2: Fix typo in example at function header for __bitmap_parselist() > V3: Fix typo in commit log and also typo at example > --- > lib/bitmap.c | 44 ++++++++++++++++++++++++++++++++++++++++---- > 1 files changed, 40 insertions(+), 4 deletions(-) > > diff --git a/lib/bitmap.c b/lib/bitmap.c > index c66da50..bccfd87 100644 > --- a/lib/bitmap.c > +++ b/lib/bitmap.c > @@ -496,6 +496,9 @@ EXPORT_SYMBOL(bitmap_print_to_pagebuf); > * ranges. Consecutively set bits are shown as two hyphen-separated > * decimal numbers, the smallest and largest bit numbers set in > * the range. > + * Optionally each range can be postfixed to denote that only parts of it > + * should be set. The parts are the range of reminders modulo some value. > + * i.e. range%mod=rem_range e.g. 0-1023%256=0-1 ==> 0,1,256,257,512,513,768,769 > * > * Returns 0 on success, -errno on invalid input strings. > * Error values: > @@ -507,12 +510,14 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen, > int is_user, unsigned long *maskp, > int nmaskbits) > { > - unsigned a, b; > + unsigned int a, b, old_a, old_b, mod_val, mod_a, mod_b; > int c, old_c, totaldigits, ndigits; > const char __user __force *ubuf = (const char __user __force *)buf; > int at_start, in_range; > > totaldigits = c = 0; > + old_a = old_b = 0; > + mod_val = mod_a = mod_b = 0; > bitmap_zero(maskp, nmaskbits); > do { > at_start = 1; > @@ -547,6 +552,23 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen, > if ((totaldigits != ndigits) && isspace(old_c)) > return -EINVAL; > > + if (c == '=') { > + mod_val = a; > + at_start = 1; > + in_range = 0; > + a = b = 0; > + continue; > + } > + > + if (c == '%') { > + old_a = a; > + old_b = b; > + at_start = 1; > + in_range = 0; > + a = b = 0; > + continue; > + } > + > if (c == '-') { > if (at_start || in_range) > return -EINVAL; > @@ -567,17 +589,31 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen, > } > if (ndigits == totaldigits) > continue; > + if (mod_val) { > + mod_a = a; > + mod_b = b; > + a = old_a; > + b = old_b; > + old_a = old_b = 0; > + } > /* if no digit is after '-', it's wrong*/ > if (at_start && in_range) > return -EINVAL; > - if (!(a <= b)) > + if (!(a <= b) || !(mod_a <= mod_b)) > return -EINVAL; > - if (b >= nmaskbits) > + if (b >= nmaskbits || (mod_val && (mod_b >= mod_val))) > return -ERANGE; > while (a <= b) { > - set_bit(a, maskp); > + if (mod_val) { > + unsigned int rem = a % mod_val; > + > + if (rem >= mod_a && rem <= mod_b) > + set_bit(a, maskp); > + } else > + set_bit(a, maskp); > a++; > } > + mod_val = mod_a = mod_b = 0; > } while (buflen && c == ','); > return 0; > } >