lkml.org 
[lkml]   [1999]   [Mar]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch] __volatile__ needed in get_cycles()?
On Wed, 31 Mar 1999, Andrea Arcangeli wrote:
> I am not talking about bugs, I am simply talking about precise profiling
> of the asm between two get_cycles_serialized(). Note, I always thought
> from time zero that get_cycles_serialized() is not needed at all for
> production code, but Tigran asked for an additional get_cycles() that
> would take care of reordering issues and since it looked fun I implemented
> it :).
Well, originally - I merely pointed out that __volatile__ is needed in
get_cycles() of 2.2.4 and it was accepted in 2.2.5. It was also said that
with
__volatile__ get_cycles() can be used for profiling but the word I chose
was "pseudo-profiling" because of the speculative execution nature of P6
family. To make "pseudo-profiling" a real "profiling" a separate version
of get_cycles() would be needed (i.e. not to cause unneeded overhead in
the current use in schedule()/SMP) and you implemented various forms of
it (since it looked fun :).

Regards,
Tigran.


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:51    [W:0.040 / U:0.548 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site