use BPF_HISTOGRAM

README.md

@@ -24,7 +24,7 @@ summary is returned to user-level.
 # ./bitehist.py 
 Tracing... Hit Ctrl-C to end.
 ^C
-     value           : count     distribution
+     kbytes          : count     distribution
        0 -> 1        : 3        |                                      |
        2 -> 3        : 0        |                                      |
        4 -> 7        : 211      |**********                            |

examples/bitehist.c

@@ -13,13 +13,10 @@
 #include <uapi/linux/ptrace.h>
 #include <linux/blkdev.h>
 
-BPF_TABLE("array", int, u64, dist, 64);
+BPF_HISTOGRAM(dist);
 
 int kprobe__blk_account_io_completion(struct pt_regs *ctx, struct request *req)
 {
-	int index = bpf_log2l(req->__data_len / 1024);
-	u64 *leaf = dist.lookup(&index);
-	if (leaf) (*leaf)++;
-
+	dist.increment(bpf_log2l(req->__data_len / 1024));
 	return 0;
 }

examples/vfsreadlat.c

@@ -13,7 +13,7 @@
 #include <uapi/linux/ptrace.h>
 
 BPF_HASH(start, u32);
-BPF_TABLE("array", int, u64, dist, 64);
+BPF_HISTOGRAM(dist);
 
 int do_entry(struct pt_regs *ctx)
 {
@@ -36,9 +36,7 @@ int do_return(struct pt_regs *ctx)
 
 	if (tsp != 0) {
 		delta = bpf_ktime_get_ns() - *tsp;
-		int index = bpf_log2l(delta / 1000);
-		u64 *leaf = dist.lookup(&index);
-		if (leaf) (*leaf)++;
+		dist.increment(bpf_log2l(delta / 1000));
 		start.delete(&pid);
 	}
 

tools/funclatency

@@ -62,8 +62,8 @@ bpf_text = """
 #include <uapi/linux/ptrace.h>
 #include <linux/blkdev.h>
 
-BPF_TABLE(\"array\", int, u64, dist, 64);
 BPF_HASH(start, u32);
+BPF_HISTOGRAM(dist);
 
 int trace_func_entry(struct pt_regs *ctx)
 {
@@ -91,9 +91,7 @@ int trace_func_return(struct pt_regs *ctx)
 	FACTOR
 
 	// store as histogram
-	int index = bpf_log2l(delta);
-	u64 *leaf = dist.lookup(&index);
-	if (leaf) (*leaf)++;
+	dist.increment(bpf_log2l(delta));
 
 	return 0;
 }