linux-kernel - Re: [PATCH v6 09/24] x86/resctrl: Use set_bit()/clear

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Message-ID: <a7933189-5bcd-e979-1d33-544186a438a5@arm.com>
Date:   Thu, 5 Oct 2023 18:07:27 +0100
From:   James Morse <james.morse@....com>
To:     babu.moger@....com, x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        shameerali.kolothum.thodi@...wei.com,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        carl@...amperecomputing.com, lcherian@...vell.com,
        bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
        xingxin.hx@...nanolis.org, baolin.wang@...ux.alibaba.com,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
        dfustini@...libre.com, amitsinght@...vell.com
Subject: Re: [PATCH v6 09/24] x86/resctrl: Use set_bit()/clear_bit() instead
 of open coding

Hi Babu,

On 04/10/2023 21:38, Moger, Babu wrote:
> On 9/14/23 12:21, James Morse wrote:
>> The resctrl CLOSID allocator uses a single 32bit word to track which
>> CLOSID are free. The setting and clearing of bits is open coded.
>>
>> A subsequent patch adds resctrl_closid_is_free(), which adds more open
>> coded bitmaps operations. These will eventually need changing to use
>> the bitops helpers so that a CLOSID bitmap of the correct size can be
>> allocated dynamically.
>>
>> Convert the existing open coded bit manipulations of closid_free_map
>> to use set_bit() and friends.

>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index ac1a6437469f..fa449ee0d1a7 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -106,7 +106,7 @@ void rdt_staged_configs_clear(void)
>>   * - Our choices on how to configure each resource become progressively more
>>   *   limited as the number of resources grows.
>>   */
>> -static int closid_free_map;
>> +static unsigned long closid_free_map;
>>  static int closid_free_map_len;
>>  
>>  int closids_supported(void)
>> @@ -126,7 +126,7 @@ static void closid_init(void)
>>  	closid_free_map = BIT_MASK(rdt_min_closid) - 1;
>>  
>>  	/* CLOSID 0 is always reserved for the default group */
>> -	closid_free_map &= ~1;
>> +	clear_bit(0, &closid_free_map);
> 
> How about using RESCTRL_RESERVED_CLOSID instead of 0 here?

Great idea - even more readable.


Thanks,

James