svn commit: r270806 - head/sys/dev/ixl

[Bjoern A. Zeeb]

On 29 Aug 2014, at 17:14 , Konstantin Belousov <kostikbel at gmail.com> wrote:

> On Fri, Aug 29, 2014 at 12:40:01PM +0000, Bjoern A. Zeeb wrote:
>> Author: bz
>> Date: Fri Aug 29 12:40:01 2014
>> New Revision: 270806
>> URL: http://svnweb.freebsd.org/changeset/base/270806
>> 
>> Log:
>>  Properly handle prefetch only for amd64 and i386 as we do elsewhere.
>> 
>>  In general theraven is right that we should factr this out and provide
>>  a general and per-arch implementation that everything can use.
>> 
>>  MFC after:	3 days
>>  X-MFC with:	r270755
>> 
>> Modified:
>>  head/sys/dev/ixl/i40e_osdep.h
>> 
>> Modified: head/sys/dev/ixl/i40e_osdep.h
>> ==============================================================================
>> --- head/sys/dev/ixl/i40e_osdep.h	Fri Aug 29 11:18:54 2014	(r270805)
>> +++ head/sys/dev/ixl/i40e_osdep.h	Fri Aug 29 12:40:01 2014	(r270806)
>> @@ -137,11 +137,15 @@ struct i40e_spinlock {
>> 
>> #define le16_to_cpu 
>> 
>> +#if defined(__amd64__) || defined(i386)
>> static __inline
>> void prefetch(void *x)
>> {
>> 	__asm volatile("prefetcht0 %0" :: "m" (*(unsigned long *)x));
>> }
> This only fix the build failure, but the code is still somewhat wrong.
> 
> Availability of the prefetch instruction depends on the presence of SSE.

We have quite a few of these as-are in the tree already;  I guess they all need fixing.


> Althought it is probably impossible to find a machine where the intended
> hardware can operate and which does not support SSE _currently_, I am
> not sure that it is wise to hard-code SSE instructions in the i386
> kernel.
> 
> Might be, a change of the compilation test from both amd64 and i386 to
> just amd64 is due.  I doubt that anybody would use 40Gb with 32bit OS,
> and even if somebody does, that the performace is at the stake in
> this case.
> 

I think going with David’s suggestion to do the right thing and centralise them somewhere so everything can use it is the proper way forward.  I think there’s also a __builtin_prefetch().


>> +#else
>> +#define	prefetch(x)
>> +#endif
>> 
>> struct i40e_osdep
>> {

— 
Bjoern A. Zeeb             "Come on. Learn, goddamn it.", WarGames, 1983