From 8434caf5890e98a06b36a7ad17b19c45ae46a922 Mon Sep 17 00:00:00 2001
From: Sage Weil <sage@newdream.net>
Date: Sun, 1 Apr 2012 16:24:39 -0700
Subject: [PATCH] qa: test_rewrite_latency

Tool to measure latency of overwriting a single block.

Signed-off-by: Sage Weil <sage@newdream.net>
---
 src/Makefile.am                  |  4 +++
 src/test/test_rewrite_latency.cc | 46 ++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)
 create mode 100644 src/test/test_rewrite_latency.cc

diff --git a/src/Makefile.am b/src/Makefile.am
index a37392d436fcf..c14b0e80cb33c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -177,6 +177,10 @@ test_mutate_SOURCES = test/test_mutate.cc
 test_mutate_LDADD = libglobal.la librados.la $(PTHREAD_LIBS) -lm $(CRYPTO_LIBS) $(EXTRALIBS)
 bin_DEBUGPROGRAMS += test_mutate
 
+test_rewrite_latency_SOURCES = test/test_rewrite_latency.cc
+test_rewrite_latency_LDADD = libcommon.la $(PTHREAD_LIBS) -lm $(CRYPTO_LIBS) $(EXTRALIBS)
+bin_DEBUGPROGRAMS += test_rewrite_latency
+
 testmsgr_SOURCES = testmsgr.cc
 testmsgr_LDADD = $(LIBGLOBAL_LDA)
 bin_DEBUGPROGRAMS += testmsgr
diff --git a/src/test/test_rewrite_latency.cc b/src/test/test_rewrite_latency.cc
new file mode 100644
index 0000000000000..5b006f9cde56d
--- /dev/null
+++ b/src/test/test_rewrite_latency.cc
@@ -0,0 +1,46 @@
+
+#include <unistd.h>
+#include <map>
+#include <errno.h>
+
+#include "include/utime.h"
+#include "common/Clock.h"
+#include "common/errno.h"
+
+using namespace std;
+
+int main(int argc, const char **argv)
+{
+  const char *fn = argv[1];
+  multimap<utime_t, utime_t> latency;
+  unsigned max = 10;
+
+  int fd = ::open(fn, O_CREAT|O_RDWR, 0644);
+  if (fd < 1) {
+    int err = errno;
+    cerr << "failed to open " << fn << " with " << cpp_strerror(err) << std::endl;
+    return -1;
+  }
+
+  while (true) {
+    utime_t now = ceph_clock_now(NULL);
+    ::pwrite(fd, fn, strlen(fn), 0);
+    utime_t lat = ceph_clock_now(NULL);
+    lat -= now;
+    utime_t oldmin;
+    if (!latency.empty())
+      oldmin = latency.begin()->first;
+    latency.insert(make_pair(lat, now));
+    utime_t newmin = latency.begin()->first;
+    while (latency.size() > max)
+      latency.erase(latency.begin());
+    if (oldmin == newmin) {
+      cout << "latency\tat" << std::endl;
+      for (multimap<utime_t,utime_t>::reverse_iterator p = latency.rbegin();
+	   p != latency.rend();
+	   ++p) {
+	cout << p->first << "\t" << p->second << std::endl;
+      }
+    }
+  }
+}
-- 
2.39.5