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Date: Wed, 22 Dec 2021 08:54:00 +0800
From: Yanling Song <songyl@ramaxel.com>
To: Stephen Hemminger <stephen@networkplumber.org>
CC: <dev@dpdk.org>, <yanling.song@linux.dev>, <yanggan@ramaxel.com>,
 <ferruh.yigit@intel.com>, <xuyun@ramaxel.com>
Subject: Re: [PATCH v1 01/25] drivers/net: introduce a new PMD driver
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On Sun, 19 Dec 2021 11:40:31 -0800
Stephen Hemminger <stephen@networkplumber.org> wrote:

> On Sat, 18 Dec 2021 10:51:28 +0800
> Yanling Song <songyl@ramaxel.com> wrote:
> 
> > +#ifdef CLOCK_MONOTONIC_RAW /* Defined in glibc bits/time.h */
> > +#define CLOCK_TYPE CLOCK_MONOTONIC_RAW
> > +#else
> > +#define CLOCK_TYPE CLOCK_MONOTONIC
> > +#endif  
> 
> CLOCK_MONOTONIC_RAW was defined in Linux.2.6.28
> DPDK does not support any kernels that old, so the #ifdef is not
> needed.
> 
OK. #ifdef will be removed in the next version.

> 
> +
> +static inline unsigned long clock_gettime_ms(void)
> +{
> +	struct timespec tv;
> +
> +	(void)clock_gettime(CLOCK_TYPE, &tv);
> +
> +	return (unsigned long)tv.tv_sec * SPNIC_S_TO_MS_UNIT +
> +	       (unsigned long)tv.tv_nsec / SPNIC_S_TO_NS_UNIT;
> +}
> 
> If all you want is jiffie accuracy,  you could use
> CLOCK_MONOTONIC_COARSE.
> 
I did not get your point: CLOCK_MONOTONIC is more accurate than
CLOCK_MONOTONIC_COARSE, right?

> 
> +#define jiffies	clock_gettime_ms()
> +#define msecs_to_jiffies(ms)	(ms)
> 
> +#define time_before(now, end)	((now) < (end))
> 
> Does that simple version of the macro work right if jiffies wraps
> around? Less of an issue on 64 bit platforms...
> 
> The kernel version is effectively.
> #define time_before(now, end) ((long)((now) - (end)) < 0)
OK. Will be changed in the next version.