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Date: Sun, 17 Jul 2016 21:59:21 +0800
From: Pan Xinhui <xinhui@...ux.vnet.ibm.com>
To: Noam Camus <noamca@...lanox.com>, decot@...glers.com
Cc: ben@...adent.org.uk, davem@...emloft.net,
akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] lib/bitmap.c: enhance bitmap syntax
在 16/7/17 21:50, Pan Xinhui 写道:
>
>
> 在 16/7/17 16:10, Noam Camus 写道:
>> From: Noam Camus <noamca@...lanox.com>
>>
>> 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.:
>> <cpus range>%modulo=<range of reminders>
>>
>> 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.
>
sorry, typos.
generic -> generate.
>> Note that this patch is backward compatible with current syntax.
>>
>> Signed-off-by: Noam Camus <noamca@...lanox.com>
>> ---
>> 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;
>> }
>>
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