From: Stephen Hemminger <stephen@networkplumber.org>
To: Vivien Didelot <vivien.didelot@gmail.com>
Cc: dev@dpdk.org, Ferruh Yigit <ferruh.yigit@intel.com>,
patrick.keroulas@radio-canada.ca, thomas@monjalon.net
Subject: Re: [dpdk-dev] [PATCH v2] net/pcap: support software Tx nanosecond timestamps
Date: Tue, 9 Jun 2020 12:43:57 -0700 [thread overview]
Message-ID: <20200609124357.20e7b4ea@hermes.lan> (raw)
In-Reply-To: <20200609190719.105323-1-vivien.didelot@gmail.com>
On Tue, 9 Jun 2020 15:07:19 -0400
Vivien Didelot <vivien.didelot@gmail.com> wrote:
>
> +#define NSEC_PER_SEC 1000000000L
> +
> static inline void
> calculate_timestamp(struct timeval *ts) {
> uint64_t cycles;
> @@ -294,8 +296,14 @@ calculate_timestamp(struct timeval *ts) {
>
> cycles = rte_get_timer_cycles() - start_cycles;
> cur_time.tv_sec = cycles / hz;
> - cur_time.tv_usec = (cycles % hz) * 1e6 / hz;
> - timeradd(&start_time, &cur_time, ts);
> + cur_time.tv_usec = (cycles % hz) * NSEC_PER_SEC / hz;
> +
> + ts->tv_sec = start_time.tv_sec + cur_time.tv_sec;
> + ts->tv_usec = start_time.tv_usec + cur_time.tv_usec;
> + if (ts->tv_usec >= NSEC_PER_SEC) {
> + ts->tv_usec -= NSEC_PER_SEC;
> + ts->tv_sec += 1;
> + }
> }
>
You may want to pre-compute the reciprocal here to save the expensive
cost of divide in the fast path. See rte_reciprocal.
next prev parent reply other threads:[~2020-06-09 19:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-09 19:07 [dpdk-dev] [PATCH v2] net/pcap: support software Tx nanosecond timestamps Vivien Didelot
2020-06-09 19:43 ` Stephen Hemminger [this message]
2020-06-09 19:57 ` Vivien Didelot
2020-06-10 12:17 ` Ferruh Yigit
2020-06-10 13:42 ` Ferruh Yigit
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