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Date: Mon, 22 Apr 2024 11:09:52 +0200
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Subject: Re: [PATCH v2 1/4] virtio_balloon: separate vm events into a function
To: zhenwei pi <pizhenwei@bytedance.com>, linux-kernel@vger.kernel.org,
 linux-mm@kvack.org, virtualization@lists.linux.dev
Cc: mst@redhat.com, jasowang@redhat.com, xuanzhuo@linux.alibaba.com,
 akpm@linux-foundation.org
References: <20240422074254.1440457-1-pizhenwei@bytedance.com>
 <20240422074254.1440457-2-pizhenwei@bytedance.com>
 <6a182645-1f7f-4b7d-a16a-36e9b1684c58@redhat.com>
 <537ac244-74b2-42ad-97a7-475ec27f2134@bytedance.com>
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From: David Hildenbrand <david@redhat.com>
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Organization: Red Hat
In-Reply-To: <537ac244-74b2-42ad-97a7-475ec27f2134@bytedance.com>
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On 22.04.24 10:04, zhenwei pi wrote:
> 
> 
> 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. :)

But for #1? :)

I mean, you didn't compile the code in your brain when you sent out v1 :P

But I agree that moving that to a separate function ins cleaner, staring 
at resulting update_balloon_stats().

Let me comment on some nits as a fresh reply.

-- 
Cheers,

David / dhildenb