Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH v4 1/5] getcpu_cache system call: cache CPU number of running thread | Date | Mon, 29 Feb 2016 14:08:34 +0100 |
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On Monday 29 February 2016 12:41:49 Mathieu Desnoyers wrote: > ----- On Feb 29, 2016, at 5:39 AM, Arnd Bergmann arnd@arndb.de wrote:
> > What's making things worse is that on some architectures, adding > > __packed will force access by bytes rather than just reading > > a 32-bit or 64-bit numbers directly, so it's slow and non-atomic. > > Agreed that many architectures issue slower instructions when reading > from packed structures, which is unwanted. > > Could we require that each field be naturally aligned and require that > they are placed so _no_ padding whatsoever should ever be added by the > compiler ? If that's possible, then we could remove the packed.
Yes, I think that is a reasonable requirement.
Arnd
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