Messages in this thread | | | Subject | Re: [PATCH 2/2] blk-iocost: Use alloc_percpu_gfp() to simplify the code | From | Baolin Wang <> | Date | Fri, 11 Dec 2020 15:13:29 +0800 |
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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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