linux-kernel - Re: Re: [PATCH v2 1/4] virtio_balloon: separate vm events into a function

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Message-ID: <537ac244-74b2-42ad-97a7-475ec27f2134@bytedance.com>
Date: Mon, 22 Apr 2024 16:04:03 +0800
From: zhenwei pi <pizhenwei@...edance.com>
To: David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, virtualization@...ts.linux.dev
Cc: mst@...hat.com, jasowang@...hat.com, xuanzhuo@...ux.alibaba.com,
 akpm@...ux-foundation.org
Subject: Re: Re: [PATCH v2 1/4] virtio_balloon: separate vm events into a
 function



On 4/22/24 15:47, David Hildenbrand wrote:
> On 22.04.24 09:42, zhenwei pi wrote:
>> All the VM events related statistics have dependence on
>> 'CONFIG_VM_EVENT_COUNTERS', once any stack variable is required by any
>> VM events in future, we would have codes like:
>>   #ifdef CONFIG_VM_EVENT_COUNTERS
>>        unsigned long foo;
>>   #endif
>>        ...
>>   #ifdef CONFIG_VM_EVENT_COUNTERS
>>        foo = events[XXX] + events[YYY];
>>        update_stat(vb, idx++, VIRTIO_BALLOON_S_XXX, foo);
>>   #endif
>>
>> Separate vm events into a single function, also remove
> 
> Why not simply use __maybe_unused for that variable?
> 

1>
static unsigned int update_balloon_stats()
{
     unsigned __maybe_unused long foo;

     ...
#ifdef CONFIG_VM_EVENT_COUNTERS
     foo = events[XXX] + events[YYY];
     update_stat(vb, idx++, VIRTIO_BALLOON_S_XXX, foo);
#endif
}

2>
static inline unsigned int update_balloon_vm_stats()
{
#ifdef CONFIG_VM_EVENT_COUNTERS
     unsigned long foo;

     foo = events[XXX] + events[YYY];
     update_stat(vb, idx++, VIRTIO_BALLOON_S_XXX, foo);
#endif
}

 From the point of my view, I don't need to compile code in my brain 
when reading codes for case 2. :)

-- 
zhenwei pi