netdev - [PATCH bpf 1/2] tools: bpftool: improve accuracy of load time

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Message-Id: <20180614180656.14550-2-jakub.kicinski@netronome.com>
Date:   Thu, 14 Jun 2018 11:06:55 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     alexei.starovoitov@...il.com, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH bpf 1/2] tools: bpftool: improve accuracy of load time

BPF program load time is reported from the kernel relative to boot time.
If conversion to wall clock does not take nanosecond parts into account,
the load time reported by bpftool may differ by one second from run to
run.  This means JSON object reported by bpftool for a program will
randomly change.

Fixes: 71bb428fe2c1 ("tools: bpf: add bpftool")
Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@...ronome.com>
---
 tools/bpf/bpftool/prog.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index a4f435203fef..05f42a46d6ed 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -90,7 +90,9 @@ static void print_boot_time(__u64 nsecs, char *buf, unsigned int size)
 	}
 
 	wallclock_secs = (real_time_ts.tv_sec - boot_time_ts.tv_sec) +
-		nsecs / 1000000000;
+		(real_time_ts.tv_nsec - boot_time_ts.tv_nsec + nsecs) /
+		1000000000;
+
 
 	if (!localtime_r(&wallclock_secs, &load_tm)) {
 		snprintf(buf, size, "%llu", nsecs / 1000000000);
-- 
2.17.1