Messages in this thread | | | Date | Tue, 11 Apr 2023 10:29:06 +0530 | From | Kautuk Consul <> | Subject | Re: [PATCH] KVM: PPC: BOOK3S: book3s_hv_nested.c: improve branch prediction for k.alloc |
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On 2023-04-07 09:01:29, Sean Christopherson wrote: > On Fri, Apr 07, 2023, Bagas Sanjaya wrote: > > On Fri, Apr 07, 2023 at 05:31:47AM -0400, Kautuk Consul wrote: > > > I used the unlikely() macro on the return values of the k.alloc > > > calls and found that it changes the code generation a bit. > > > Optimize all return paths of k.alloc calls by improving > > > branch prediction on return value of k.alloc. > > Nit, this is improving code generation, not branch prediction. Sorry my mistake. > > > What about below? > > > > "Improve branch prediction on kmalloc() and kzalloc() call by using > > unlikely() macro to optimize their return paths." > > Another nit, using unlikely() doesn't necessarily provide a measurable optimization. > As above, it does often improve code generation for the happy path, but that doesn't > always equate to improved performance, e.g. if the CPU can easily predict the branch > and/or there is no impact on the cache footprint. I see. I will submit a v2 of the patch with a better and more accurate description. Does anyone else have any comments before I do so ?
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