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SubjectRe: [PATCH 2/2] blk-iocost: Use alloc_percpu_gfp() to simplify the code
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Hi Tejun,

> Hello,
>
> On Thu, Dec 10, 2020 at 06:56:45PM +0800, Baolin Wang wrote:
>> Use alloc_percpu_gfp() with __GFP_ZERO flag, which can remove
>> some explicit initialization code.
>
> __GFP_ZERO is implicit for percpu allocations and local[64]_t's initial
> states aren't guaranteed to be all zeros on different archs.

Thanks for teaching me this, at least I did not get this from the
local_ops Documentation before. Just out of curiosity, these local[64]_t
variables are also allocated from budy allocator ultimately, why they
can not be initialized to zeros on some ARCHs with __GFP_ZERO? Could you
elaborate on about this restriction? Thanks.

By the way, seems the kyber-iosched has the same issue, since the
'struct kyber_cpu_latency' also contains an atomic_t variable.

kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,
GFP_KERNEL | __GFP_ZERO);
if (!kqd->cpu_latency)
goto err_kqd;

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