[ovs-dev] [PATCH RFC 5/5] dpif-netdev: Prefetch the cacheline having the cycle stats.

[Bodireddy, Bhanuprakash]

>
>> Prefetch the cacheline having the cycle stats so that we can speed up
>> the cycles_count_start() and cycles_count_intermediate().
>
>Do you have any performance results?

I don’t have nos. for this patch alone. I was testing the overall throughput along with other patches (that were *not* part of this RFC series) to verify performance improvements. I will include in commit log when I do for individual patches. 

BTW, I usually look at  the % of total instructions getting retired, cycles spent in front and back-end for the functions to see if prefetching does improve/degrade performance.

- Bhanuprakash.

>
>>
>> Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy at
>> intel.com>
>> ---
>>  lib/dpif-netdev.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c index
>> b74b5d7..ab13d83 100644
>> --- a/lib/dpif-netdev.c
>> +++ b/lib/dpif-netdev.c
>> @@ -576,7 +576,7 @@ struct dp_netdev_pmd_thread {
>>          struct ovs_mutex flow_mutex;
>>          /* 8 pad bytes. */
>>      );
>> -    PADDED_MEMBERS(CACHE_LINE_SIZE,
>> +    PADDED_MEMBERS_CACHELINE_MARKER(CACHE_LINE_SIZE,
>cachelineC,
>>          struct cmap flow_table OVS_GUARDED; /* Flow table. */
>>
>>          /* One classifier per in_port polled by the pmd */ @@ -4082,6
>> +4082,7 @@ reload:
>>          lc = UINT_MAX;
>>      }
>>
>> +    OVS_PREFETCH_CACHE(&pmd->cachelineC, OPCH_HTW);
>>      cycles_count_start(pmd);
>>      for (;;) {
>>          for (i = 0; i < poll_cnt; i++) {
>> --
>> 2.4.11