Merged!
Maxim.
On 01/12/2016 15:22, Savolainen, Petri (Nokia - FI/Espoo) wrote:
Ping.
*From:*EXT Bill Fischofer [mailto:bill.fischo...@linaro.org]
*Sent:* Thursday, January 07, 2016 2:30 PM
*To:* Savolainen, Petri (Nokia - FI/Espoo)
*Cc:* LNG ODP Mailman List
*Subject:* Re: [lng-odp] [API-NEXT PATCH 5/5] linux-generic: removed
spin_internal
OK, thanks.
For this Series:
Reviewed-by: Bill Fischofer <bill.fischo...@linaro.org
<mailto:bill.fischo...@linaro.org>>
On Thu, Jan 7, 2016 at 6:21 AM, Savolainen, Petri (Nokia - FI/Espoo)
<petri.savolai...@nokia.com <mailto:petri.savolai...@nokia.com>> wrote:
*From:*EXT Bill Fischofer [mailto:bill.fischo...@linaro.org
<mailto:bill.fischo...@linaro.org>]
*Sent:* Thursday, January 07, 2016 2:11 PM
*To:* Savolainen, Petri (Nokia - FI/Espoo)
*Cc:* LNG ODP Mailman List
*Subject:* Re: [lng-odp] [API-NEXT PATCH 5/5] linux-generic:
removed spin_internal
On Thu, Jan 7, 2016 at 2:50 AM, Savolainen, Petri (Nokia -
FI/Espoo) <petri.savolai...@nokia.com
<mailto:petri.savolai...@nokia.com>> wrote:
*From:*lng-odp [mailto:lng-odp-boun...@lists.linaro.org
<mailto:lng-odp-boun...@lists.linaro.org>] *On Behalf Of *EXT
Savolainen, Petri (Nokia - FI/Espoo)
*Sent:* Thursday, January 07, 2016 10:44 AM
*To:* EXT Bill Fischofer
*Cc:* LNG ODP Mailman List
*Subject:* Re: [lng-odp] [API-NEXT PATCH 5/5] linux-generic:
removed spin_internal
*From:*EXT Bill Fischofer [mailto:bill.fischo...@linaro.org]
*Sent:* Tuesday, January 05, 2016 8:01 PM
*To:* Savolainen, Petri (Nokia - FI/Espoo)
*Cc:* LNG ODP Mailman List
*Subject:* Re: [lng-odp] [API-NEXT PATCH 5/5] linux-generic:
removed spin_internal
diff --git a/platform/linux-generic/odp_barrier.c
b/platform/linux-generic/odp_barrier.c
index 53d83c0..0bfc0f0 100644
--- a/platform/linux-generic/odp_barrier.c
+++ b/platform/linux-generic/odp_barrier.c
@@ -6,7 +6,7 @@
#include <odp/barrier.h>
#include <odp/sync.h>
-#include <odp_spin_internal.h>
+#include <odp/cpu.h>
#include <odp_atomic_internal.h>
void odp_barrier_init(odp_barrier_t *barrier, int count)
@@ -43,7 +43,7 @@ void odp_barrier_wait(odp_barrier_t
*barrier)
} else {
while ((odp_atomic_load_u32(&barrier->bar) < barrier->count)
== wasless)
- odp_spin();
+ odp_cpu_pause();
Why wouldn't you just want to change the implementation of
odp_spin() to use the pause instruction here? These are spin
lock waits but nowhere does ODP specify that spins must be
implemented inefficiently.
Since odp_cpu_pause() is intended for exactly this use case,
it’s better to use the call also internally to highlight the
correct usage (and eat our own dog food).
The implementation is arch specific (“pause” vs. “nop” vs.
empty). For example, on multi-core x86 “pause” improves lock
performance since CPUs are not stressing the interconnect at
100% speed. Pause instruction was designed for this use case.
-Petri
Also odp_cpu_pause() is implemented as static inline function
- so there’s no function call, it will be the “pause”
instruction directly.
I agree completely with the implementation change for all the
reasons you cite, just questioning why it needs to be reflected in
an API name change that implies a specific implementation. What if
SoC X doesn't have a pause instruction but instead uses a delay
instruction or some other technique for efficient waiting?
odp_spin() is as good a "neutral" name as any to say "I don't
have anything to do here other than delay for a bit". We expect
each ODP API to be implemented as efficiently as possible, and on
X86 that means using the native pause instruction, so that's just
how odp_spin() would be implemented here. It would also be an
inline function on this architecture.
odp_spin() was an internal function, not an API. Odp_cpu_pause()
is a new API call. It does not do any spinning but pauses the cpu
for a very short while. Actual spin logic calls the pause. It’s in
the API so that when application implements its own lock-free, etc
algorithms it can also pause within its spin loop.
-Petri
-Petri
}
_ODP_FULL_BARRIER();
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