lkml.org 
[lkml]   [2016]   [Feb]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH v4 1/5] getcpu_cache system call: cache CPU number of running thread
Date
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

\
 
 \ /
  Last update: 2016-02-29 14:41    [W:0.132 / U:0.424 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site