[dpdk-dev] [PATCH] examples/timer: fix incorrect time interval
Thomas Monjalon
thomas at monjalon.net
Wed May 5 23:37:29 CEST 2021
15/04/2021 09:12, Min Hu (Connor):
> From: Chengchang Tang <tangchengchang at 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: stable at dpdk.org
>
> Signed-off-by: Chengchang Tang <tangchengchang at huawei.com>
> Signed-off-by: Min Hu (Connor) <humin29 at 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.
> + * 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();
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