[iproute2-next,1/3] tc: support conversions to or from 64 bit nanosecond-based time

Message ID 20180806170953.164776-2-ysseung@google.com
State Changes Requested
Delegated to: David Ahern
Headers show
Series
  • support delivering packets in delayed
Related show

Commit Message

Yousuk Seung Aug. 6, 2018, 5:09 p.m.
From: Dave Taht <dave.taht@gmail.com>

Using a 32 bit field to represent time in nanoseconds results in a
maximum value of about 4.3 seconds, which is well below many observed
delays in WiFi and LTE, and barely in the ballpark for a trip past the
Earth's moon, Luna.

Using 64 bit time fields in nanoseconds allows us to simulate
network diameters of several hundred light-years. However, only
conversions to and from ns, us, ms, and seconds are provided.

Signed-off-by: Yousuk Seung <ysseung@google.com>
Signed-off-by: Dave Taht <dave.taht@gmail.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
---
 tc/tc_core.h |  4 ++++
 tc/tc_util.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 tc/tc_util.h |  3 +++
 3 files changed, 62 insertions(+)

Comments

David Ahern Aug. 12, 2018, 10:09 p.m. | #1
On 8/6/18 11:09 AM, Yousuk Seung wrote:
> diff --git a/tc/tc_core.h b/tc/tc_core.h
> index 1dfa9a4f773b..a0fe0923d171 100644
> --- a/tc/tc_core.h
> +++ b/tc/tc_core.h
> @@ -7,6 +7,10 @@
>  
>  #define TIME_UNITS_PER_SEC	1000000
>  
> +#define NSEC_PER_USEC 1000
> +#define NSEC_PER_MSEC 1000000
> +#define NSEC_PER_SEC 1000000000LL
> +

These are not specific to tc so a header in include is a better location
(utils.h or a new one)

>  enum link_layer {
>  	LINKLAYER_UNSPEC,
>  	LINKLAYER_ETHERNET,
> diff --git a/tc/tc_util.c b/tc/tc_util.c
> index d7578528a31b..c39c9046dcae 100644
> --- a/tc/tc_util.c
> +++ b/tc/tc_util.c

Similarly for these time functions - not specific to tc so move to
lib/utils.c

> @@ -385,6 +385,61 @@ char *sprint_ticks(__u32 ticks, char *buf)
>  	return sprint_time(tc_core_tick2time(ticks), buf);
>  }
>  
> +/* 64 bit times are represented internally in nanoseconds */
> +int get_time64(__s64 *time, const char *str)

__u64 seems more appropriate than __s64

> +{
> +	double nsec;
> +	char *p;
> +
> +	nsec = strtod(str, &p);
> +	if (p == str)
> +		return -1;
> +
> +	if (*p) {
> +		if (strcasecmp(p, "s") == 0 ||
> +		    strcasecmp(p, "sec") == 0 ||
> +		    strcasecmp(p, "secs") == 0)
> +			nsec *= NSEC_PER_SEC;
> +		else if (strcasecmp(p, "ms") == 0 ||
> +			 strcasecmp(p, "msec") == 0 ||
> +			 strcasecmp(p, "msecs") == 0)
> +			nsec *= NSEC_PER_MSEC;
> +		else if (strcasecmp(p, "us") == 0 ||
> +			 strcasecmp(p, "usec") == 0 ||
> +			 strcasecmp(p, "usecs") == 0)
> +			nsec *= NSEC_PER_USEC;
> +		else if (strcasecmp(p, "ns") == 0 ||
> +			 strcasecmp(p, "nsec") == 0 ||
> +			 strcasecmp(p, "nsecs") == 0)

strncasecmp would be more efficient

> +			nsec *= 1;
> +		else
> +			return -1;
> +	}
> +
> +	*time = nsec;
> +	return 0;
> +}
> +
> +void print_time64(char *buf, int len, __s64 time)
> +{
> +	double nsec = time;
> +
> +	if (time >= NSEC_PER_SEC)
> +		snprintf(buf, len, "%.3fs", nsec/NSEC_PER_SEC);
> +	else if (time >= NSEC_PER_MSEC)
> +		snprintf(buf, len, "%.3fms", nsec/NSEC_PER_MSEC);
> +	else if (time >= NSEC_PER_USEC)
> +		snprintf(buf, len, "%.3fus", nsec/NSEC_PER_USEC);
> +	else
> +		snprintf(buf, len, "%lldns", time);
> +}
> +
> +char *sprint_time64(__s64 time, char *buf)
> +{
> +	print_time64(buf, SPRINT_BSIZE-1, time);
> +	return buf;
> +}
> +
>  int get_size(unsigned int *size, const char *str)
>  {
>  	double sz;
Dave Taht Aug. 13, 2018, 6:37 p.m. | #2
On Sun, Aug 12, 2018 at 3:09 PM David Ahern <dsahern@gmail.com> wrote:
>
> On 8/6/18 11:09 AM, Yousuk Seung wrote:
> > diff --git a/tc/tc_core.h b/tc/tc_core.h
> > index 1dfa9a4f773b..a0fe0923d171 100644
> > --- a/tc/tc_core.h
> > +++ b/tc/tc_core.h
> > @@ -7,6 +7,10 @@
> >
> >  #define TIME_UNITS_PER_SEC   1000000
> >
> > +#define NSEC_PER_USEC 1000
> > +#define NSEC_PER_MSEC 1000000
> > +#define NSEC_PER_SEC 1000000000LL
> > +
>
> These are not specific to tc so a header in include is a better location
> (utils.h or a new one)
>
> >  enum link_layer {
> >       LINKLAYER_UNSPEC,
> >       LINKLAYER_ETHERNET,
> > diff --git a/tc/tc_util.c b/tc/tc_util.c
> > index d7578528a31b..c39c9046dcae 100644
> > --- a/tc/tc_util.c
> > +++ b/tc/tc_util.c
>
> Similarly for these time functions - not specific to tc so move to
> lib/utils.c
>
> > @@ -385,6 +385,61 @@ char *sprint_ticks(__u32 ticks, char *buf)
> >       return sprint_time(tc_core_tick2time(ticks), buf);
> >  }
> >
> > +/* 64 bit times are represented internally in nanoseconds */
> > +int get_time64(__s64 *time, const char *str)
>
> __u64 seems more appropriate than __s64

The reason why these are signed is to leave room in the API to
print/manage negative values. Wasting the 64th bit thusly would only
matter after extreme uptimes.

There was something of a long debate on this when these patches went
around the first time. We ended up with signed time in the netem code
also.


> > +{
> > +     double nsec;
> > +     char *p;
> > +
> > +     nsec = strtod(str, &p);
> > +     if (p == str)
> > +             return -1;
> > +
> > +     if (*p) {
> > +             if (strcasecmp(p, "s") == 0 ||
> > +                 strcasecmp(p, "sec") == 0 ||
> > +                 strcasecmp(p, "secs") == 0)
> > +                     nsec *= NSEC_PER_SEC;
> > +             else if (strcasecmp(p, "ms") == 0 ||
> > +                      strcasecmp(p, "msec") == 0 ||
> > +                      strcasecmp(p, "msecs") == 0)
> > +                     nsec *= NSEC_PER_MSEC;
> > +             else if (strcasecmp(p, "us") == 0 ||
> > +                      strcasecmp(p, "usec") == 0 ||
> > +                      strcasecmp(p, "usecs") == 0)
> > +                     nsec *= NSEC_PER_USEC;
> > +             else if (strcasecmp(p, "ns") == 0 ||
> > +                      strcasecmp(p, "nsec") == 0 ||
> > +                      strcasecmp(p, "nsecs") == 0)
>
> strncasecmp would be more efficient
>
> > +                     nsec *= 1;
> > +             else
> > +                     return -1;
> > +     }
> > +
> > +     *time = nsec;
> > +     return 0;
> > +}
> > +
> > +void print_time64(char *buf, int len, __s64 time)
> > +{
> > +     double nsec = time;
> > +
> > +     if (time >= NSEC_PER_SEC)
> > +             snprintf(buf, len, "%.3fs", nsec/NSEC_PER_SEC);
> > +     else if (time >= NSEC_PER_MSEC)
> > +             snprintf(buf, len, "%.3fms", nsec/NSEC_PER_MSEC);
> > +     else if (time >= NSEC_PER_USEC)
> > +             snprintf(buf, len, "%.3fus", nsec/NSEC_PER_USEC);
> > +     else
> > +             snprintf(buf, len, "%lldns", time);
> > +}
> > +
> > +char *sprint_time64(__s64 time, char *buf)
> > +{
> > +     print_time64(buf, SPRINT_BSIZE-1, time);
> > +     return buf;
> > +}
> > +
> >  int get_size(unsigned int *size, const char *str)
> >  {
> >       double sz;

Patch

diff --git a/tc/tc_core.h b/tc/tc_core.h
index 1dfa9a4f773b..a0fe0923d171 100644
--- a/tc/tc_core.h
+++ b/tc/tc_core.h
@@ -7,6 +7,10 @@ 
 
 #define TIME_UNITS_PER_SEC	1000000
 
+#define NSEC_PER_USEC 1000
+#define NSEC_PER_MSEC 1000000
+#define NSEC_PER_SEC 1000000000LL
+
 enum link_layer {
 	LINKLAYER_UNSPEC,
 	LINKLAYER_ETHERNET,
diff --git a/tc/tc_util.c b/tc/tc_util.c
index d7578528a31b..c39c9046dcae 100644
--- a/tc/tc_util.c
+++ b/tc/tc_util.c
@@ -385,6 +385,61 @@  char *sprint_ticks(__u32 ticks, char *buf)
 	return sprint_time(tc_core_tick2time(ticks), buf);
 }
 
+/* 64 bit times are represented internally in nanoseconds */
+int get_time64(__s64 *time, const char *str)
+{
+	double nsec;
+	char *p;
+
+	nsec = strtod(str, &p);
+	if (p == str)
+		return -1;
+
+	if (*p) {
+		if (strcasecmp(p, "s") == 0 ||
+		    strcasecmp(p, "sec") == 0 ||
+		    strcasecmp(p, "secs") == 0)
+			nsec *= NSEC_PER_SEC;
+		else if (strcasecmp(p, "ms") == 0 ||
+			 strcasecmp(p, "msec") == 0 ||
+			 strcasecmp(p, "msecs") == 0)
+			nsec *= NSEC_PER_MSEC;
+		else if (strcasecmp(p, "us") == 0 ||
+			 strcasecmp(p, "usec") == 0 ||
+			 strcasecmp(p, "usecs") == 0)
+			nsec *= NSEC_PER_USEC;
+		else if (strcasecmp(p, "ns") == 0 ||
+			 strcasecmp(p, "nsec") == 0 ||
+			 strcasecmp(p, "nsecs") == 0)
+			nsec *= 1;
+		else
+			return -1;
+	}
+
+	*time = nsec;
+	return 0;
+}
+
+void print_time64(char *buf, int len, __s64 time)
+{
+	double nsec = time;
+
+	if (time >= NSEC_PER_SEC)
+		snprintf(buf, len, "%.3fs", nsec/NSEC_PER_SEC);
+	else if (time >= NSEC_PER_MSEC)
+		snprintf(buf, len, "%.3fms", nsec/NSEC_PER_MSEC);
+	else if (time >= NSEC_PER_USEC)
+		snprintf(buf, len, "%.3fus", nsec/NSEC_PER_USEC);
+	else
+		snprintf(buf, len, "%lldns", time);
+}
+
+char *sprint_time64(__s64 time, char *buf)
+{
+	print_time64(buf, SPRINT_BSIZE-1, time);
+	return buf;
+}
+
 int get_size(unsigned int *size, const char *str)
 {
 	double sz;
diff --git a/tc/tc_util.h b/tc/tc_util.h
index 6632c4f9c528..87be951c622d 100644
--- a/tc/tc_util.h
+++ b/tc/tc_util.h
@@ -82,12 +82,14 @@  int get_percent_rate64(__u64 *rate, const char *str, const char *dev);
 int get_size(unsigned int *size, const char *str);
 int get_size_and_cell(unsigned int *size, int *cell_log, char *str);
 int get_time(unsigned int *time, const char *str);
+int get_time64(__s64 *time, const char *str);
 int get_linklayer(unsigned int *val, const char *arg);
 
 void print_rate(char *buf, int len, __u64 rate);
 void print_size(char *buf, int len, __u32 size);
 void print_qdisc_handle(char *buf, int len, __u32 h);
 void print_time(char *buf, int len, __u32 time);
+void print_time64(char *buf, int len, __s64 time);
 void print_linklayer(char *buf, int len, unsigned int linklayer);
 void print_devname(enum output_type type, int ifindex);
 
@@ -96,6 +98,7 @@  char *sprint_size(__u32 size, char *buf);
 char *sprint_qdisc_handle(__u32 h, char *buf);
 char *sprint_tc_classid(__u32 h, char *buf);
 char *sprint_time(__u32 time, char *buf);
+char *sprint_time64(__s64 time, char *buf);
 char *sprint_ticks(__u32 ticks, char *buf);
 char *sprint_linklayer(unsigned int linklayer, char *buf);