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[ovs-dev,v2] dpif-netdev-perf: Accurate cycle counter update

Message ID 20191205170420.53947-1-malvika.gupta@arm.com
State Accepted
Headers show
Series [ovs-dev,v2] dpif-netdev-perf: Accurate cycle counter update | expand

Commit Message

Malvika Gupta Dec. 5, 2019, 5:04 p.m. UTC 
The accurate timing implementation in this patch gets the wall clock counter via
cntvct_el0 register access. This call is portable to all aarch64 architectures
and has been verified on an 64-bit arm server.

Suggested-by: Yanqin Wei <yanqin.wei@arm.com>
Signed-off-by: Malvika Gupta <malvika.gupta@arm.com>
Reviewed-by: Ilya Maximets <i.maximets@ovn.org>
---
v2:
- Updated patch subject to remove redundant words and enhance clarity.
- Modify code to write directly to s->last_tsc instead of writing to a local
  variable first and then assigning it to s->last_tsc.
---
 lib/dpif-netdev-perf.h | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Ilya Maximets Dec. 6, 2019, 4:13 p.m. UTC | #1 
On 05.12.2019 18:04, Malvika Gupta wrote:
> The accurate timing implementation in this patch gets the wall clock counter via
> cntvct_el0 register access. This call is portable to all aarch64 architectures
> and has been verified on an 64-bit arm server.
> 
> Suggested-by: Yanqin Wei <yanqin.wei@arm.com>
> Signed-off-by: Malvika Gupta <malvika.gupta@arm.com>
> Reviewed-by: Ilya Maximets <i.maximets@ovn.org>

Thanks!  I don't see any replies on a mail-list, but it
looks like Ben applied this patch to master.

Best regards, Ilya Maximets.
diff mbox series

Patch

diff --git a/lib/dpif-netdev-perf.h b/lib/dpif-netdev-perf.h
index ce369375b..72645b6b3 100644
--- a/lib/dpif-netdev-perf.h
+++ b/lib/dpif-netdev-perf.h
@@ -220,6 +220,10 @@  cycles_counter_update(struct pmd_perf_stats *s)
     asm volatile("rdtsc" : "=a" (l), "=d" (h));
 
     return s->last_tsc = ((uint64_t) h << 32) | l;
+#elif !defined(_MSC_VER) && defined(__aarch64__)
+    asm volatile("mrs %0, cntvct_el0" : "=r" (s->last_tsc));
+
+    return s->last_tsc;
 #elif defined(__linux__)
     return rdtsc_syscall(s);
 #else