diff mbox

[dpdk-dev,3/3] app/test: enable test_red to build on non x86 platform

Message ID 1439901605-31164-4-git-send-email-jerin.jacob@caviumnetworks.com (mailing list archive)
State Superseded, archived
Headers

Commit Message

Jerin Jacob Aug. 18, 2015, 12:40 p.m. UTC 
Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
---
 app/test/test_red.c | 2 ++
 1 file changed, 2 insertions(+)

Comments

Thomas Monjalon Aug. 25, 2015, 12:03 p.m. UTC | #1 
2015-08-18 18:10, Jerin Jacob:
> --- a/app/test/test_red.c
> +++ b/app/test/test_red.c
> +#if defined(RTE_ARCH_X86_64) || defined(RTE_ARCH_I686) || defined(RTE_ARCH_X86_X32)
>  #ifdef __PIC__
>      asm volatile (
>      "mov %%ebx, %%edi\n"
> @@ -155,6 +156,7 @@ static inline void rdtsc_prof_start(struct rdtsc_prof *p)
>  #else
>  	asm( "cpuid" : : : "%eax", "%ebx", "%ecx", "%edx" );
>  #endif
> +#endif
>  	p->clk_start = rte_rdtsc();

The right fix would be to move that arch-specific code into an EAL abstraction.
Jerin Jacob Aug. 27, 2015, 4:08 a.m. UTC | #2 
On Tue, Aug 25, 2015 at 02:03:13PM +0200, Thomas Monjalon wrote:
> 2015-08-18 18:10, Jerin Jacob:
> > --- a/app/test/test_red.c
> > +++ b/app/test/test_red.c
> > +#if defined(RTE_ARCH_X86_64) || defined(RTE_ARCH_I686) || defined(RTE_ARCH_X86_X32)
> >  #ifdef __PIC__
> >      asm volatile (
> >      "mov %%ebx, %%edi\n"
> > @@ -155,6 +156,7 @@ static inline void rdtsc_prof_start(struct rdtsc_prof *p)
> >  #else
> >  	asm( "cpuid" : : : "%eax", "%ebx", "%ecx", "%edx" );
> >  #endif
> > +#endif
> >  	p->clk_start = rte_rdtsc();
> 
> The right fix would be to move that arch-specific code into an EAL abstraction.

I agree. I thought the same. But I am not able to understand why 'cpuid'
instruction used here without any input/output parameters. What is the
role of 'cpuid' instruction in this specific function and what to
abstract in eal ?
 
>
Thomas Monjalon Aug. 27, 2015, 9:04 a.m. UTC | #3 
2015-08-27 09:38, Jerin Jacob:
> On Tue, Aug 25, 2015 at 02:03:13PM +0200, Thomas Monjalon wrote:
> > 2015-08-18 18:10, Jerin Jacob:
> > > --- a/app/test/test_red.c
> > > +++ b/app/test/test_red.c
> > > +#if defined(RTE_ARCH_X86_64) || defined(RTE_ARCH_I686) || defined(RTE_ARCH_X86_X32)
> > >  #ifdef __PIC__
> > >      asm volatile (
> > >      "mov %%ebx, %%edi\n"
> > > @@ -155,6 +156,7 @@ static inline void rdtsc_prof_start(struct rdtsc_prof *p)
> > >  #else
> > >  	asm( "cpuid" : : : "%eax", "%ebx", "%ecx", "%edx" );
> > >  #endif
> > > +#endif
> > >  	p->clk_start = rte_rdtsc();
> > 
> > The right fix would be to move that arch-specific code into an EAL abstraction.
> 
> I agree. I thought the same. But I am not able to understand why 'cpuid'
> instruction used here without any input/output parameters. What is the
> role of 'cpuid' instruction in this specific function and what to
> abstract in eal ?

It is explained here:
	http://dpdk.org/ml/archives/dev/2014-January/001182.html

I think it can be replaced by rte_rdtsc_precise() which was implemented
after the above discussion. It uses rte_mb instead of cpuid.

As explained in the following thread, memory fence can be used instead of cpuid:
	http://stackoverflow.com/a/12634857
As showed in the following threads, rdtscp can also be used:
	http://stackoverflow.com/a/27697754
	http://dpdk.org/ml/archives/dev/2015-April/016770.html

It reminds me that we should deprecate rte_rdtsc() and rte_get_tsc_cycles() in
favor of a more generic name, e.g. rte_get_clock_cycles().
diff mbox

Patch

diff --git a/app/test/test_red.c b/app/test/test_red.c
index 262df72..813c508 100644
--- a/app/test/test_red.c
+++ b/app/test/test_red.c
@@ -146,6 +146,7 @@  static void rdtsc_prof_init(struct rdtsc_prof *p, const char *name)
 
 static inline void rdtsc_prof_start(struct rdtsc_prof *p)
 {
+#if defined(RTE_ARCH_X86_64) || defined(RTE_ARCH_I686) || defined(RTE_ARCH_X86_X32)
 #ifdef __PIC__
     asm volatile (
     "mov %%ebx, %%edi\n"
@@ -155,6 +156,7 @@  static inline void rdtsc_prof_start(struct rdtsc_prof *p)
 #else
 	asm( "cpuid" : : : "%eax", "%ebx", "%ecx", "%edx" );
 #endif
+#endif
 	p->clk_start = rte_rdtsc();
 }