On 2021/5/6 5:37, Thomas Monjalon wrote:
> 15/04/2021 09:12, Min Hu (Connor):
>> From: Chengchang Tang <tangchengch...@huawei.com>
>>
>> Timer sample example assumes that the frequency of the timer is about
>> 2Ghz to control the period of calling rte_timer_manage(). But this
>> assumption is easy to fail. For example. the frequency of tsc on ARM64
>> is much less than 2Ghz.
>>
>> This patch uses the frequency of the current timer to calculate the
>> correct time interval to ensure consistent result on all platforms.
>>
>> In addition, the rte_rdtsc() is replaced with the more recommended
>> rte_get_timer_cycles function in this patch.
>>
>> Fixes: af75078fece3 ("first public release")
>> Cc: sta...@dpdk.org
>>
>> Signed-off-by: Chengchang Tang <tangchengch...@huawei.com>
>> Signed-off-by: Min Hu (Connor) <humi...@huawei.com>
> [...]
>> /*
>> - * Call the timer handler on each core: as we don't
>> - * need a very precise timer, so only call
>> - * rte_timer_manage() every ~10ms (at 2Ghz). In a real
>> - * application, this will enhance performances as
>> - * reading the HPET timer is not efficient.
>> + * Call the timer handler on each core: as we don't need a
>> + * very precise timer, so only call rte_timer_manage()
>> + * every ~10ms. since rte_eal_hpet_init() has not been
>> + * called, the rte_rdtsc() will be used at runtime.
>
> I don't understand this last sentence.
>
This is explaining why we can use rte_get_timer_cycles() instead of rte_rdtsc().
In this example, we call tsc to improve its performance. So, we invoked
rte_rdtsc()
here. Now the function rte_get_timer_cycles() encapsulates these counters. It
will
invoke the corresponding counter according to the user's initialization of the
counter.
>> + * In a real application, this will enhance performances
>> + * as reading the HPET timer is not efficient.
>> */
>> - cur_tsc = rte_rdtsc();
>> + cur_tsc = rte_get_timer_cycles();
>
>
>
>
> .
>
