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-rw-r--r--samples/bpf/tracex3.bpf.c100
1 files changed, 100 insertions, 0 deletions
diff --git a/samples/bpf/tracex3.bpf.c b/samples/bpf/tracex3.bpf.c
new file mode 100644
index 0000000000..41f37966f5
--- /dev/null
+++ b/samples/bpf/tracex3.bpf.c
@@ -0,0 +1,100 @@
+/* Copyright (c) 2013-2015 PLUMgrid, http://plumgrid.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ */
+#include "vmlinux.h"
+#include <linux/version.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct start_key {
+ dev_t dev;
+ u32 _pad;
+ sector_t sector;
+};
+
+struct {
+ __uint(type, BPF_MAP_TYPE_HASH);
+ __type(key, long);
+ __type(value, u64);
+ __uint(max_entries, 4096);
+} my_map SEC(".maps");
+
+/* from /sys/kernel/tracing/events/block/block_io_start/format */
+SEC("tracepoint/block/block_io_start")
+int bpf_prog1(struct trace_event_raw_block_rq *ctx)
+{
+ u64 val = bpf_ktime_get_ns();
+ struct start_key key = {
+ .dev = ctx->dev,
+ .sector = ctx->sector
+ };
+
+ bpf_map_update_elem(&my_map, &key, &val, BPF_ANY);
+ return 0;
+}
+
+static unsigned int log2l(unsigned long long n)
+{
+#define S(k) if (n >= (1ull << k)) { i += k; n >>= k; }
+ int i = -(n == 0);
+ S(32); S(16); S(8); S(4); S(2); S(1);
+ return i;
+#undef S
+}
+
+#define SLOTS 100
+
+struct {
+ __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+ __uint(key_size, sizeof(u32));
+ __uint(value_size, sizeof(u64));
+ __uint(max_entries, SLOTS);
+} lat_map SEC(".maps");
+
+/* from /sys/kernel/tracing/events/block/block_io_done/format */
+SEC("tracepoint/block/block_io_done")
+int bpf_prog2(struct trace_event_raw_block_rq *ctx)
+{
+ struct start_key key = {
+ .dev = ctx->dev,
+ .sector = ctx->sector
+ };
+
+ u64 *value, l, base;
+ u32 index;
+
+ value = bpf_map_lookup_elem(&my_map, &key);
+ if (!value)
+ return 0;
+
+ u64 cur_time = bpf_ktime_get_ns();
+ u64 delta = cur_time - *value;
+
+ bpf_map_delete_elem(&my_map, &key);
+
+ /* the lines below are computing index = log10(delta)*10
+ * using integer arithmetic
+ * index = 29 ~ 1 usec
+ * index = 59 ~ 1 msec
+ * index = 89 ~ 1 sec
+ * index = 99 ~ 10sec or more
+ * log10(x)*10 = log2(x)*10/log2(10) = log2(x)*3
+ */
+ l = log2l(delta);
+ base = 1ll << l;
+ index = (l * 64 + (delta - base) * 64 / base) * 3 / 64;
+
+ if (index >= SLOTS)
+ index = SLOTS - 1;
+
+ value = bpf_map_lookup_elem(&lat_map, &index);
+ if (value)
+ *value += 1;
+
+ return 0;
+}
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;