Messages in this thread |  | | Subject | Re: [PATCH] mm/page_alloc: make calling prep_compound_head more reliable | From | Miaohe Lin <> | Date | Thu, 16 Jun 2022 11:21:55 +0800 |
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On 2022/6/15 20:42, Matthew Wilcox wrote: > On Wed, Jun 15, 2022 at 03:44:06PM +0800, Miaohe Lin wrote: >>> We definitely don't need the unlikely here. >> >> Could you please give me a more detailed explanation? IIUC, the above if condition >> will only meet at a probability of 1/512. So unlikely tells the compiler to do some >> optimization around it. Or am I miss something? > > Only add unlikely() when the compiler can't figure out for itself that > it's unlikely. You should also check the generated code and/or > benchmark the results to be sure that it's actually an improvement. > Using unlikely() needs to be backed up with more than just a feeling.
I see. Many thanks for clarifying. Will keep it in mind. :)
> > . >
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