0003-io_u-fix-rate-limiting-to-handle-file-wrap-around.patch

From 970d9000a32a57b7a18333ec612e1a19276b0c87 Mon Sep 17 00:00:00 2001
From: Ken Barr <kenbarr@google.com>
Date: Fri, 3 Jan 2020 15:11:44 -0500
Subject: [PATCH 23/77] io_u: fix rate limiting to handle file wrap-around

When using "rate" with "time_based", the amount of time to sleep should be based
on the invocation time (epoch) rather than the start time of a given loop
(start) because no other statistics are reset when a file is re-opened.
Prior to this change, a wrap-around would cause the rate_ddir code to compute
that ~0 time had elapsed since the last I/O (i.e., a near-infinite rate), and
trigger a very long sleep in an attempt to adjust to the given rate.

Testing done:
  Using configuration below...
    Before: starts at 100 MB/sec and drops to 0 after ~10 sec (upon wrap) before
    recovering at t ~ 20.
    After: maintains 100 MB/sec for the duration of the test

  [repro]
  # 1 GiB + 1 Byte, to force a fill_io_u failure, the file to close and
  # reopen, and the start timestamp to reset.
  size=1073741825
  bs=2097152
  direct=1
  ioengine=psync
  readwrite=write

  runtime=30s
  time_based
  rate=100m

  filename=data_file
---
 io_u.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_u.c b/io_u.c
index b5c3133..4a0c725 100644
--- a/io_u.c
+++ b/io_u.c
@@ -644,7 +644,7 @@ static enum fio_ddir rate_ddir(struct thread_data *td, enum fio_ddir ddir)
 	uint64_t now;
 
 	assert(ddir_rw(ddir));
-	now = utime_since_now(&td->start);
+	now = utime_since_now(&td->epoch);
 
 	/*
 	 * if rate_next_io_time is in the past, need to catch up to rate
-- 
1.8.3.1