linux-kernel - Re: [PATCH v6 04/21] x86/resctrl: Group struct rdt_hw

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Date:   Thu, 8 Sep 2022 18:01:04 +0100
From:   James Morse <james.morse@....com>
To:     haoxin <xhao@...ux.alibaba.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>,
        Babu Moger <Babu.Moger@....com>,
        shameerali.kolothum.thodi@...wei.com,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        lcherian@...vell.com, bobo.shaobowang@...wei.com,
        tan.shaopeng@...itsu.com, Jamie Iles <quic_jiles@...cinc.com>,
        Cristian Marussi <cristian.marussi@....com>,
        xingxin.hx@...nanolis.org, baolin.wang@...ux.alibaba.com
Subject: Re: [PATCH v6 04/21] x86/resctrl: Group struct rdt_hw_domain cleanup

Hi Hao Xin,

On 07/09/2022 07:28, haoxin wrote:
> 
> 在 2022/9/2 下午11:48, James Morse 写道:
>> domain_add_cpu() and domain_remove_cpu() need to kfree() the child
>> arrays that were allocated by domain_setup_ctrlval().
>>
>> As this memory is moved around, and new arrays are created, adjusting
>> the error handling cleanup code becomes noisier.
>>
>> To simplify this, move all the kfree() calls into a domain_free() helper.
>> This depends on struct rdt_hw_domain being kzalloc()d, allowing it to
>> unconditionally kfree() all the child arrays.

>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
>> index 25f30148478b..e37889f7a1a5 100644
>> --- a/arch/x86/kernel/cpu/resctrl/core.c
>> +++ b/arch/x86/kernel/cpu/resctrl/core.c
>> @@ -414,6 +414,13 @@ void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm)
>>       }
>>   }
>>   +static void domain_free(struct rdt_hw_domain *hw_dom)

> add inline ?

It's best to let the compiler decide this. As this is in a C file, and is declared static,
the compiler is free to duplicate and inline this function as it sees fit. The inline
keyword would only be needed if this were in a header file.

Looking at the built object file - the compiler chose not to duplicate this into the two
callers, presumably because of the size of the function.

Unless its relied on for correctness, or is a performance sensitive path, its best to let
the compiler make its own decision here.


Thanks,

James


>> +{
>> +    kfree(hw_dom->ctrl_val);
>> +    kfree(hw_dom->mbps_val);
>> +    kfree(hw_dom);
>> +}
>> +
>>   static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
>>   {
>>       struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);