trafgen: Alloc cpus according to specified number of packets

Trafgen uses all the online CPUs even if the number of packets specified
by -n is less than the number of selected CPUs. Such behaviour leads to
issues:

    - trafgen re-calculates number of packets per CPU which
      leads to rounding it to 0 then no packets will be sent.

    - trafgen might send more packets than specified by -n because
      of using all the online cpus.

Fixed by taking min(#CPUs, #packets) as the number of CPUs if a number
of packets is specified by -n.

Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
[tklauser: moved code and added explanatory comment]
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

1 files changed, 8 insertions, 0 deletions

diff --git a/trafgen.c b/trafgen.c
index 22264cb..deef1f2 100644
--- a/trafgen.c
+++ b/trafgen.c
@@ -1070,6 +1070,14 @@ int main(int argc, char **argv)
 		sleep(0);
 	}
 
+	/*
+	 * If number of packets is smaller than number of CPUs use only as
+	 * many CPUs as there are packets. Otherwise we end up sending more
+	 * packets than intended or none at all.
+	 */
+	if (ctx.num)
+		ctx.cpus = min_t(unsigned int, ctx.num, ctx.cpus);
+
 	irq = device_irq_number(ctx.device);
 	if (set_irq_aff)
 		device_set_irq_affinity_list(irq, 0, ctx.cpus - 1);