examples/tracing/bitehist.py: add example of linear histogram
Add an example of linear histogram, which might be useful to newcomers.
And also update the comments.
# bitehist.py Block I/O size histogram.
# For Linux, uses BCC, eBPF. Embedded C.
#
-# Written as a basic example of using a histogram to show a distribution.
+# Written as a basic example of using histograms to show a distribution.
#
-# The default interval is 5 seconds. A Ctrl-C will print the partially
-# gathered histogram then exit.
+# A Ctrl-C will print the gathered histogram then exit.
#
# Copyright (c) 2015 Brendan Gregg.
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 15-Aug-2015 Brendan Gregg Created this.
+# 03-Feb-2019 Xiaozhou Liu added linear histogram.
from __future__ import print_function
from bcc import BPF
@@ -23,10 +23,12 @@ b = BPF(text="""
#include <linux/blkdev.h>
BPF_HISTOGRAM(dist);
+BPF_HISTOGRAM(dist_linear);
int kprobe__blk_account_io_completion(struct pt_regs *ctx, struct request *req)
{
dist.increment(bpf_log2l(req->__data_len / 1024));
+ dist_linear.increment(req->__data_len / 1024);
return 0;
}
""")
@@ -41,4 +43,10 @@ except KeyboardInterrupt:
print()
# output
+print("log2 histogram")
+print("~~~~~~~~~~~~~~")
b["dist"].print_log2_hist("kbytes")
+
+print("\nlinear histogram")
+print("~~~~~~~~~~~~~~~~")
+b["dist_linear"].print_linear_hist("kbytes")
