From 2d0b929f36446398dbda6c18cb2eaa03495c320c Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@scylladb.com>
Date: Sun, 28 Feb 2016 19:40:27 +0200
Subject: [PATCH] Refactor test to allow concurrent append tests as well

---
 fsqual.cc | 42 ++++++++++++++++++++++++++++++------------
 1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/fsqual.cc b/fsqual.cc
index fcf2c99..90552d3 100644
--- a/fsqual.cc
+++ b/fsqual.cc
@@ -12,6 +12,8 @@
 #include <cstdlib>
 #include <type_traits>
 #include <functional>
+#include <vector>
+#include <algorithm>
 
 template <typename Counter, typename Func>
 typename std::result_of<Func()>::type
@@ -34,30 +36,46 @@ with_ctxsw_counting(Counter& counter, Func&& func) {
     return func();
 }
 
-void test_append(io_context_t ioctx, int fd) {
+void test_concurrent_append(io_context_t ioctx, int fd, unsigned iodepth) {
     auto nr = 1000;
     auto bufsize = 4096;
     auto ctxsw = 0;
     auto buf = aligned_alloc(4096, 4096);
-    for (int i = 0; i < nr; ++i) {
-        struct iocb cmd;
-        io_prep_pwrite(&cmd, fd, buf, bufsize, bufsize*i);
-        struct iocb* cmds[1] = { &cmd };
-        with_ctxsw_counting(ctxsw, [&] {
-            io_submit(ioctx, 1, cmds);
-        });
-        struct io_event ioev;
-        io_getevents(ioctx, 1, 1, &ioev, nullptr);
+    auto current_depth = unsigned(0);
+    auto initiated = 0;
+    auto completed = 0;
+    auto iocbs = std::vector<iocb>(iodepth);
+    auto iocbps = std::vector<iocb*>(iodepth);
+    std::iota(iocbps.begin(), iocbps.end(), iocbs.data());
+    auto ioevs = std::vector<io_event>(iodepth);
+    while (completed < nr) {
+        auto i = unsigned(0);
+        while (initiated < nr && current_depth < iodepth) {
+            io_prep_pwrite(&iocbs[i++], fd, buf, bufsize, bufsize*initiated++);
+            ++current_depth;
+        }
+        if (i) {
+            with_ctxsw_counting(ctxsw, [&] {
+                io_submit(ioctx, i, iocbps.data());
+            });
+        }
+        auto n = io_getevents(ioctx, 1, iodepth, ioevs.data(), nullptr);
+        current_depth -= n;
+        completed += n;
     }
     auto rate = float(ctxsw) / nr;
     auto verdict = rate < 0.1 ? "GOOD" : "BAD";
-    std::cout << "context switch per appending io: " << rate
+    std::cout << "context switch per appending io (iodepth " << iodepth << "): " << rate
           << " (" << verdict << ")\n";
 }
 
+void test_append(io_context_t ioctx, int fd) {
+    return test_concurrent_append(ioctx, fd, 1);
+}
+
 void run_test(std::function<void (io_context_t ioctx, int fd)> func) {
     io_context_t ioctx = {};
-    io_setup(1, &ioctx);
+    io_setup(128, &ioctx);
     auto fname = "fsqual.tmp";
     int fd = open(fname, O_CREAT|O_EXCL|O_RDWR|O_DIRECT, 0600);
     unlink(fname);
-- 
2.49.0