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SubjectRe: [RFC][Patch v11 1/2] mm: page_hinting: core infrastructure
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On 7/11/19 12:22 PM, Dave Hansen wrote:
> On 7/11/19 8:25 AM, Nitesh Narayan Lal wrote:
>> On 7/10/19 4:45 PM, Dave Hansen wrote:
>>> On 7/10/19 12:51 PM, Nitesh Narayan Lal wrote:
>>>> +struct zone_free_area {
>>>> + unsigned long *bitmap;
>>>> + unsigned long base_pfn;
>>>> + unsigned long end_pfn;
>>>> + atomic_t free_pages;
>>>> + unsigned long nbits;
>>>> +} free_area[MAX_NR_ZONES];
>>> Why do we need an extra data structure. What's wrong with putting
>>> per-zone data in ... 'struct zone'?
>> Will it be acceptable to add fields in struct zone, when they will only
>> be used by page hinting?
> Wait a sec... MAX_NR_ZONES the number of zone types not the maximum
> number of *zones* in the system.
>
> Did you test this on a NUMA system?
Yes, I tested it with a guest having 2 and 3 NUMA nodes.
> In any case, yes, you can put these in 'struct zone'. It will waste
> less space that way, on average, than what you have here (one you scale
> it to MAX_NR_ZONE*MAX_NUM_NODES.
>>> The cover letter claims that it
>>> doesn't touch core-mm infrastructure, but if it depends on mechanisms
>>> like this, I think that's a very bad thing.
>>>
>>> To be honest, I'm not sure this series is worth reviewing at this point.
>>> It's horribly lightly commented and full of kernel antipatterns lik
>>>
>>> void func()
>>> {
>>> if () {
>>> ... indent entire logic
>>> ... of function
>>> }
>>> }
>> I usually run checkpatch to detect such indentation issues. For the
>> patches, I shared it didn't show me any issues.
> Just because checkpatch doesn't complain does not mean it is good form.
> We write the above as:
>
> void func()
> {
> if (!something)
> goto out;
>
> ... logic of function here
> out:
> // cleanup
> }

Yeap, I got it. I will correct this.


--
Thanks
Nitesh

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