bitesize: switch to tracepoints (#2281)
bitesize: switch to tracepoints
diff --git a/man/man8/bitesize.8 b/man/man8/bitesize.8
index 07046e8..7dc8c93 100644
--- a/man/man8/bitesize.8
+++ b/man/man8/bitesize.8
@@ -6,8 +6,7 @@
.SH DESCRIPTION
Show I/O distribution for requested block sizes, by process name.
-This works by tracing block I/O kernel functions using dynamic
-tracing and prints a historgram of I/O size.
+This works by tracing block:block_rq_insert and prints a historgram of I/O size.
Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
@@ -29,7 +28,7 @@
An ASCII bar chart to visualize the distribution (count column)
.SH OVERHEAD
-This traces kernel block I/O functions to update a histgroam, which are
+This traces a block I/O tracepoint to update a histogram, which is
asynchronously copied to user-space. This method is very efficient, and
the overhead for most storage I/O rates (< 10k IOPS) should be negligible.
If you have a higher IOPS storage environment, test and quantify the overhead
diff --git a/tools/bitesize.py b/tools/bitesize.py
index f70f091..f23feec 100755
--- a/tools/bitesize.py
+++ b/tools/bitesize.py
@@ -11,6 +11,7 @@
# Licensed under the Apache License, Version 2.0 (the "License")
#
# 05-Feb-2016 Allan McAleavy ran pep8 against file
+# 19-Mar-2019 Brendan Gregg Switched to use tracepoints.
from bcc import BPF
from time import sleep
@@ -24,47 +25,21 @@
u64 slot;
};
-struct val_t {
- char name[TASK_COMM_LEN];
-};
-
BPF_HISTOGRAM(dist, struct proc_key_t);
-BPF_HASH(commbyreq, struct request *, struct val_t);
-int trace_pid_start(struct pt_regs *ctx, struct request *req)
+TRACEPOINT_PROBE(block, block_rq_insert)
{
- struct val_t val = {};
-
- if (bpf_get_current_comm(&val.name, sizeof(val.name)) == 0) {
- commbyreq.update(&req, &val);
- }
- return 0;
-}
-
-int do_count(struct pt_regs *ctx, struct request *req)
-{
- struct val_t *valp;
-
- valp = commbyreq.lookup(&req);
- if (valp == 0) {
- return 0;
- }
-
- if (req->__data_len > 0) {
- struct proc_key_t key = {.slot = bpf_log2l(req->__data_len / 1024)};
- bpf_probe_read(&key.name, sizeof(key.name),valp->name);
- dist.increment(key);
- }
+ struct proc_key_t key = {.slot = bpf_log2l(args->bytes / 1024)};
+ bpf_probe_read(&key.name, sizeof(key.name), args->comm);
+ dist.increment(key);
return 0;
}
"""
# load BPF program
b = BPF(text=bpf_text)
-b.attach_kprobe(event="blk_account_io_start", fn_name="trace_pid_start")
-b.attach_kprobe(event="blk_account_io_completion", fn_name="do_count")
-print("Tracing... Hit Ctrl-C to end.")
+print("Tracing block I/O... Hit Ctrl-C to end.")
# trace until Ctrl-C
dist = b.get_table("dist")