qht: add qht-bench, a performance benchmark

This serves as a performance benchmark as well as a stress test
for QHT. We can tweak quite a number of things, including the
number of resize threads and how frequently resizes are triggered.

A performance comparison of QHT vs CLHT[1] and ck_hs[2] using
this same benchmark program can be found here:
  http://imgur.com/a/0Bms4

The tests are run on a 64-core AMD Opteron 6376, pinning threads
to cores favoring same-socket cores. For each run, qht-bench is
invoked with:
  $ tests/qht-bench -d $duration -n $n -u $u -g $range
, where $duration is in seconds, $n is the number of threads,
$u is the update rate (0.0 to 100.0), and $range is the number
of keys.

Note that ck_hs's performance drops significantly as writes go
up, since it requires an external lock (I used a ck_spinlock)
around every write.

Also, note that CLHT instead of using a seqlock, relies on an
allocator that does not ever return the same address during the
same read-critical section. This gives it a slight performance
advantage over QHT on read-heavy workloads, since the seqlock
writes aren't there.

[1] CLHT: https://github.com/LPD-EPFL/CLHT
          https://infoscience.epfl.ch/record/207109/files/ascy_asplos15.pdf

[2] ck_hs: http://concurrencykit.org/
           http://backtrace.io/blog/blog/2015/03/13/workload-specialization/

A few of those plots are shown in text here, since that site
might not be online forever. Throughput is on Mops/s on the Y axis.

                             200K keys, 0 % updates

  450 ++--+------+------+-------+-------+-------+-------+------+-------+--++
      |   +      +      +       +       +       +       +      +      +N+  |
  400 ++                                                           ---+E+ ++
      |                                                       +++----      |
  350 ++          9 ++------+------++                       --+E+    -+H+ ++
      |             |      +H+-     |                 -+N+----   ---- +++  |
  300 ++          8 ++     +E+     ++             -----+E+  --+H+         ++
      |             |      +++      |         -+N+-----+H+--               |
  250 ++          7 ++------+------++  +++-----+E+----                    ++
  200 ++                    1         -+E+-----+H+                        ++
      |                           ----                     qht +-E--+      |
  150 ++                      -+E+                        clht +-H--+     ++
      |                   ----                              ck +-N--+      |
  100 ++               +E+                                                ++
      |            ----                                                    |
   50 ++       -+E+                                                       ++
      |   +E+E+  +      +       +       +       +       +      +       +   |
    0 ++--E------+------+-------+-------+-------+-------+------+-------+--++
          1      8      16      24      32      40      48     56      64
                                Number of threads

                             200K keys, 1 % updates

  350 ++--+------+------+-------+-------+-------+-------+------+-------+--++
      |   +      +      +       +       +       +       +      +     -+E+  |
  300 ++                                                         -----+H+ ++
      |                                                       +E+--        |
      |           9 ++------+------++                  +++----             |
  250 ++            |      +E+   -- |                 -+E+                ++
      |           8 ++         --  ++             ----                     |
  200 ++            |      +++-     |  +++  ---+E+                        ++
      |           7 ++------N------++ -+E+--               qht +-E--+      |
      |                     1  +++----                    clht +-H--+      |
  150 ++                      -+E+                          ck +-N--+     ++
      |                   ----                                             |
  100 ++               +E+                                                ++
      |            ----                                                    |
      |        -+E+                                                        |
   50 ++    +H+-+N+----+N+-----+N+------                                  ++
      |   +E+E+  +      +       +      +N+-----+N+-----+N+----+N+-----+N+  |
    0 ++--E------+------+-------+-------+-------+-------+------+-------+--++
          1      8      16      24      32      40      48     56      64
                                Number of threads

                             200K keys, 20 % updates

  300 ++--+------+------+-------+-------+-------+-------+------+-------+--++
      |   +      +      +       +       +       +       +      +       +   |
      |                                                              -+H+  |
  250 ++                                                         ----     ++
      |           9 ++------+------++                       --+H+  ---+E+  |
      |           8 ++     +H+--   ++                 -+H+----+E+--        |
  200 ++            |      +E+    --|             -----+E+--  +++         ++
      |           7 ++      + ---- ++       ---+H+---- +++ qht +-E--+      |
  150 ++          6 ++------N------++ -+H+-----+E+        clht +-H--+     ++
      |                     1     -----+E+--                ck +-N--+      |
      |                       -+H+----                                     |
  100 ++                  -----+E+                                        ++
      |                +E+--                                               |
      |            ----+++                                                 |
   50 ++       -+E+                                                       ++
      |     +E+ +++                                                        |
      |   +E+N+-+N+-----+       +       +       +       +      +       +   |
    0 ++--E------+------N-------N-------N-------N-------N------N-------N--++
          1      8      16      24      32      40      48     56      64
                                Number of threads

                            200K keys, 100 % updates       qht +-E--+
                                                          clht +-H--+
  160 ++--+------+------+-------+-------+-------+-------+---ck-+-N-----+--++
      |   +      +      +       +       +       +       +      +   ----H   |
  140 ++                                                      +H+--  -+E+ ++
      |                                                +++----   ----      |
  120 ++          8 ++------+------++                 -+H+    +E+         ++
      |           7 ++     +H+---- ++             ---- +++----             |
  100 ++            |      +E+      |  +++  ---+H+    -+E+                ++
      |           6 ++     +++     ++ -+H+--   +++----                     |
   80 ++          5 ++------N----------+E+-----+E+                        ++
      |                     1 -+H+---- +++                                 |
      |                   -----+E+                                         |
   60 ++               +H+---- +++                                        ++
      |            ----+E+                                                 |
   40 ++        +H+----                                                   ++
      |       --+E+                                                        |
   20 ++    +E+                                                           ++
      |  +EE+    +      +       +       +       +       +      +       +   |
    0 ++--+N-N---N------N-------N-------N-------N-------N------N-------N--++
          1      8      16      24      32      40      48     56      64
                                Number of threads

Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1465412133-3029-13-git-send-email-cota@braap.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

3 files changed, 491 insertions, 1 deletions

diff --git a/tests/.gitignore b/tests/.gitignore
index ffde5d2b83..d19023e41d 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -7,6 +7,7 @@ check-qnull
 check-qstring
 check-qom-interface
 check-qom-proplist
+qht-bench
 rcutorture
 test-aio
 test-base64
diff --git a/tests/Makefile.include b/tests/Makefile.include
index 429d384842..7b00301c9c 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -400,7 +400,7 @@ test-obj-y = tests/check-qint.o tests/check-qstring.o tests/check-qdict.o \
 	tests/test-opts-visitor.o tests/test-qmp-event.o \
 	tests/rcutorture.o tests/test-rcu-list.o \
 	tests/test-qdist.o \
-	tests/test-qht.o
+	tests/test-qht.o tests/qht-bench.o
 
 $(test-obj-y): QEMU_INCLUDES += -Itests
 QEMU_CFLAGS += -I$(SRC_PATH)/tests
@@ -441,6 +441,7 @@ tests/rcutorture$(EXESUF): tests/rcutorture.o $(test-util-obj-y)
 tests/test-rcu-list$(EXESUF): tests/test-rcu-list.o $(test-util-obj-y)
 tests/test-qdist$(EXESUF): tests/test-qdist.o $(test-util-obj-y)
 tests/test-qht$(EXESUF): tests/test-qht.o $(test-util-obj-y)
+tests/qht-bench$(EXESUF): tests/qht-bench.o $(test-util-obj-y)
 
 tests/test-qdev-global-props$(EXESUF): tests/test-qdev-global-props.o \
 	hw/core/qdev.o hw/core/qdev-properties.o hw/core/hotplug.o\
diff --git a/tests/qht-bench.c b/tests/qht-bench.c
new file mode 100644
index 0000000000..ad8efbca95
--- /dev/null
+++ b/tests/qht-bench.c
@@ -0,0 +1,488 @@
+/*
+ * Copyright (C) 2016, Emilio G. Cota <cota@braap.org>
+ *
+ * License: GNU GPL, version 2 or later.
+ *   See the COPYING file in the top-level directory.
+ */
+#include "qemu/osdep.h"
+#include <glib.h>
+#include "qemu/processor.h"
+#include "qemu/atomic.h"
+#include "qemu/qht.h"
+#include "qemu/rcu.h"
+#include "exec/tb-hash-xx.h"
+
+struct thread_stats {
+    size_t rd;
+    size_t not_rd;
+    size_t in;
+    size_t not_in;
+    size_t rm;
+    size_t not_rm;
+    size_t rz;
+    size_t not_rz;
+};
+
+struct thread_info {
+    void (*func)(struct thread_info *);
+    struct thread_stats stats;
+    uint64_t r;
+    bool write_op; /* writes alternate between insertions and removals */
+    bool resize_down;
+} QEMU_ALIGNED(64); /* avoid false sharing among threads */
+
+static struct qht ht;
+static QemuThread *rw_threads;
+
+#define DEFAULT_RANGE (4096)
+#define DEFAULT_QHT_N_ELEMS DEFAULT_RANGE
+
+static unsigned int duration = 1;
+static unsigned int n_rw_threads = 1;
+static unsigned long lookup_range = DEFAULT_RANGE;
+static unsigned long update_range = DEFAULT_RANGE;
+static size_t init_range = DEFAULT_RANGE;
+static size_t init_size = DEFAULT_RANGE;
+static size_t n_ready_threads;
+static long populate_offset;
+static long *keys;
+
+static size_t resize_min;
+static size_t resize_max;
+static struct thread_info *rz_info;
+static unsigned long resize_delay = 1000;
+static double resize_rate; /* 0.0 to 1.0 */
+static unsigned int n_rz_threads = 1;
+static QemuThread *rz_threads;
+
+static double update_rate; /* 0.0 to 1.0 */
+static uint64_t update_threshold;
+static uint64_t resize_threshold;
+
+static size_t qht_n_elems = DEFAULT_QHT_N_ELEMS;
+static int qht_mode;
+
+static bool test_start;
+static bool test_stop;
+
+static struct thread_info *rw_info;
+
+static const char commands_string[] =
+    " -d = duration, in seconds\n"
+    " -n = number of threads\n"
+    "\n"
+    " -o = offset at which keys start\n"
+    "\n"
+    " -g = set -s,-k,-K,-l,-r to the same value\n"
+    " -s = initial size hint\n"
+    " -k = initial number of keys\n"
+    " -K = initial range of keys (will be rounded up to pow2)\n"
+    " -l = lookup range of keys (will be rounded up to pow2)\n"
+    " -r = update range of keys (will be rounded up to pow2)\n"
+    "\n"
+    " -u = update rate (0.0 to 100.0), 50/50 split of insertions/removals\n"
+    "\n"
+    " -R = enable auto-resize\n"
+    " -S = resize rate (0.0 to 100.0)\n"
+    " -D = delay (in us) between potential resizes\n"
+    " -N = number of resize threads";
+
+static void usage_complete(int argc, char *argv[])
+{
+    fprintf(stderr, "Usage: %s [options]\n", argv[0]);
+    fprintf(stderr, "options:\n%s\n", commands_string);
+    exit(-1);
+}
+
+static bool is_equal(const void *obj, const void *userp)
+{
+    const long *a = obj;
+    const long *b = userp;
+
+    return *a == *b;
+}
+
+static inline uint32_t h(unsigned long v)
+{
+    return tb_hash_func5(v, 0, 0);
+}
+
+/*
+ * From: https://en.wikipedia.org/wiki/Xorshift
+ * This is faster than rand_r(), and gives us a wider range (RAND_MAX is only
+ * guaranteed to be >= INT_MAX).
+ */
+static uint64_t xorshift64star(uint64_t x)
+{
+    x ^= x >> 12; /* a */
+    x ^= x << 25; /* b */
+    x ^= x >> 27; /* c */
+    return x * UINT64_C(2685821657736338717);
+}
+
+static void do_rz(struct thread_info *info)
+{
+    struct thread_stats *stats = &info->stats;
+
+    if (info->r < resize_threshold) {
+        size_t size = info->resize_down ? resize_min : resize_max;
+        bool resized;
+
+        resized = qht_resize(&ht, size);
+        info->resize_down = !info->resize_down;
+
+        if (resized) {
+            stats->rz++;
+        } else {
+            stats->not_rz++;
+        }
+    }
+    g_usleep(resize_delay);
+}
+
+static void do_rw(struct thread_info *info)
+{
+    struct thread_stats *stats = &info->stats;
+    uint32_t hash;
+    long *p;
+
+    if (info->r >= update_threshold) {
+        bool read;
+
+        p = &keys[info->r & (lookup_range - 1)];
+        hash = h(*p);
+        read = qht_lookup(&ht, is_equal, p, hash);
+        if (read) {
+            stats->rd++;
+        } else {
+            stats->not_rd++;
+        }
+    } else {
+        p = &keys[info->r & (update_range - 1)];
+        hash = h(*p);
+        if (info->write_op) {
+            bool written = false;
+
+            if (qht_lookup(&ht, is_equal, p, hash) == NULL) {
+                written = qht_insert(&ht, p, hash);
+            }
+            if (written) {
+                stats->in++;
+            } else {
+                stats->not_in++;
+            }
+        } else {
+            bool removed = false;
+
+            if (qht_lookup(&ht, is_equal, p, hash)) {
+                removed = qht_remove(&ht, p, hash);
+            }
+            if (removed) {
+                stats->rm++;
+            } else {
+                stats->not_rm++;
+            }
+        }
+        info->write_op = !info->write_op;
+    }
+}
+
+static void *thread_func(void *p)
+{
+    struct thread_info *info = p;
+
+    rcu_register_thread();
+
+    atomic_inc(&n_ready_threads);
+    while (!atomic_mb_read(&test_start)) {
+        cpu_relax();
+    }
+
+    rcu_read_lock();
+    while (!atomic_read(&test_stop)) {
+        info->r = xorshift64star(info->r);
+        info->func(info);
+    }
+    rcu_read_unlock();
+
+    rcu_unregister_thread();
+    return NULL;
+}
+
+/* sets everything except info->func */
+static void prepare_thread_info(struct thread_info *info, int i)
+{
+    /* seed for the RNG; each thread should have a different one */
+    info->r = (i + 1) ^ time(NULL);
+    /* the first update will be a write */
+    info->write_op = true;
+    /* the first resize will be down */
+    info->resize_down = true;
+
+    memset(&info->stats, 0, sizeof(info->stats));
+}
+
+static void
+th_create_n(QemuThread **threads, struct thread_info **infos, const char *name,
+            void (*func)(struct thread_info *), int offset, int n)
+{
+    struct thread_info *info;
+    QemuThread *th;
+    int i;
+
+    th = g_malloc(sizeof(*th) * n);
+    *threads = th;
+
+    info = qemu_memalign(64, sizeof(*info) * n);
+    *infos = info;
+
+    for (i = 0; i < n; i++) {
+        prepare_thread_info(&info[i], offset + i);
+        info[i].func = func;
+        qemu_thread_create(&th[i], name, thread_func, &info[i],
+                           QEMU_THREAD_JOINABLE);
+    }
+}
+
+static void create_threads(void)
+{
+    th_create_n(&rw_threads, &rw_info, "rw", do_rw, 0, n_rw_threads);
+    th_create_n(&rz_threads, &rz_info, "rz", do_rz, n_rw_threads, n_rz_threads);
+}
+
+static void pr_params(void)
+{
+    printf("Parameters:\n");
+    printf(" duration:          %d s\n", duration);
+    printf(" # of threads:      %u\n", n_rw_threads);
+    printf(" initial # of keys: %zu\n", init_size);
+    printf(" initial size hint: %zu\n", qht_n_elems);
+    printf(" auto-resize:       %s\n",
+           qht_mode & QHT_MODE_AUTO_RESIZE ? "on" : "off");
+    if (resize_rate) {
+        printf(" resize_rate:       %f%%\n", resize_rate * 100.0);
+        printf(" resize range:      %zu-%zu\n", resize_min, resize_max);
+        printf(" # resize threads   %u\n", n_rz_threads);
+    }
+    printf(" update rate:       %f%%\n", update_rate * 100.0);
+    printf(" offset:            %ld\n", populate_offset);
+    printf(" initial key range: %zu\n", init_range);
+    printf(" lookup range:      %lu\n", lookup_range);
+    printf(" update range:      %lu\n", update_range);
+}
+
+static void do_threshold(double rate, uint64_t *threshold)
+{
+    if (rate == 1.0) {
+        *threshold = UINT64_MAX;
+    } else {
+        *threshold = rate * UINT64_MAX;
+    }
+}
+
+static void htable_init(void)
+{
+    unsigned long n = MAX(init_range, update_range);
+    uint64_t r = time(NULL);
+    size_t retries = 0;
+    size_t i;
+
+    /* avoid allocating memory later by allocating all the keys now */
+    keys = g_malloc(sizeof(*keys) * n);
+    for (i = 0; i < n; i++) {
+        keys[i] = populate_offset + i;
+    }
+
+    /* some sanity checks */
+    g_assert_cmpuint(lookup_range, <=, n);
+
+    /* compute thresholds */
+    do_threshold(update_rate, &update_threshold);
+    do_threshold(resize_rate, &resize_threshold);
+
+    if (resize_rate) {
+        resize_min = n / 2;
+        resize_max = n;
+        assert(resize_min < resize_max);
+    } else {
+        n_rz_threads = 0;
+    }
+
+    /* initialize the hash table */
+    qht_init(&ht, qht_n_elems, qht_mode);
+    assert(init_size <= init_range);
+
+    pr_params();
+
+    fprintf(stderr, "Initialization: populating %zu items...", init_size);
+    for (i = 0; i < init_size; i++) {
+        for (;;) {
+            uint32_t hash;
+            long *p;
+
+            r = xorshift64star(r);
+            p = &keys[r & (init_range - 1)];
+            hash = h(*p);
+            if (qht_insert(&ht, p, hash)) {
+                break;
+            }
+            retries++;
+        }
+    }
+    fprintf(stderr, " populated after %zu retries\n", retries);
+}
+
+static void add_stats(struct thread_stats *s, struct thread_info *info, int n)
+{
+    int i;
+
+    for (i = 0; i < n; i++) {
+        struct thread_stats *stats = &info[i].stats;
+
+        s->rd += stats->rd;
+        s->not_rd += stats->not_rd;
+
+        s->in += stats->in;
+        s->not_in += stats->not_in;
+
+        s->rm += stats->rm;
+        s->not_rm += stats->not_rm;
+
+        s->rz += stats->rz;
+        s->not_rz += stats->not_rz;
+    }
+}
+
+static void pr_stats(void)
+{
+    struct thread_stats s = {};
+    double tx;
+
+    add_stats(&s, rw_info, n_rw_threads);
+    add_stats(&s, rz_info, n_rz_threads);
+
+    printf("Results:\n");
+
+    if (resize_rate) {
+        printf(" Resizes:           %zu (%.2f%% of %zu)\n",
+               s.rz, (double)s.rz / (s.rz + s.not_rz) * 100, s.rz + s.not_rz);
+    }
+
+    printf(" Read:              %.2f M (%.2f%% of %.2fM)\n",
+           (double)s.rd / 1e6,
+           (double)s.rd / (s.rd + s.not_rd) * 100,
+           (double)(s.rd + s.not_rd) / 1e6);
+    printf(" Inserted:          %.2f M (%.2f%% of %.2fM)\n",
+           (double)s.in / 1e6,
+           (double)s.in / (s.in + s.not_in) * 100,
+           (double)(s.in + s.not_in) / 1e6);
+    printf(" Removed:           %.2f M (%.2f%% of %.2fM)\n",
+           (double)s.rm / 1e6,
+           (double)s.rm / (s.rm + s.not_rm) * 100,
+           (double)(s.rm + s.not_rm) / 1e6);
+
+    tx = (s.rd + s.not_rd + s.in + s.not_in + s.rm + s.not_rm) / 1e6 / duration;
+    printf(" Throughput:        %.2f MT/s\n", tx);
+    printf(" Throughput/thread: %.2f MT/s/thread\n", tx / n_rw_threads);
+}
+
+static void run_test(void)
+{
+    unsigned int remaining;
+    int i;
+
+    while (atomic_read(&n_ready_threads) != n_rw_threads + n_rz_threads) {
+        cpu_relax();
+    }
+    atomic_mb_set(&test_start, true);
+    do {
+        remaining = sleep(duration);
+    } while (remaining);
+    atomic_mb_set(&test_stop, true);
+
+    for (i = 0; i < n_rw_threads; i++) {
+        qemu_thread_join(&rw_threads[i]);
+    }
+    for (i = 0; i < n_rz_threads; i++) {
+        qemu_thread_join(&rz_threads[i]);
+    }
+}
+
+static void parse_args(int argc, char *argv[])
+{
+    int c;
+
+    for (;;) {
+        c = getopt(argc, argv, "d:D:g:k:K:l:hn:N:o:r:Rs:S:u:");
+        if (c < 0) {
+            break;
+        }
+        switch (c) {
+        case 'd':
+            duration = atoi(optarg);
+            break;
+        case 'D':
+            resize_delay = atol(optarg);
+            break;
+        case 'g':
+            init_range = pow2ceil(atol(optarg));
+            lookup_range = pow2ceil(atol(optarg));
+            update_range = pow2ceil(atol(optarg));
+            qht_n_elems = atol(optarg);
+            init_size = atol(optarg);
+            break;
+        case 'h':
+            usage_complete(argc, argv);
+            exit(0);
+        case 'k':
+            init_size = atol(optarg);
+            break;
+        case 'K':
+            init_range = pow2ceil(atol(optarg));
+            break;
+        case 'l':
+            lookup_range = pow2ceil(atol(optarg));
+            break;
+        case 'n':
+            n_rw_threads = atoi(optarg);
+            break;
+        case 'N':
+            n_rz_threads = atoi(optarg);
+            break;
+        case 'o':
+            populate_offset = atol(optarg);
+            break;
+        case 'r':
+            update_range = pow2ceil(atol(optarg));
+            break;
+        case 'R':
+            qht_mode |= QHT_MODE_AUTO_RESIZE;
+            break;
+        case 's':
+            qht_n_elems = atol(optarg);
+            break;
+        case 'S':
+            resize_rate = atof(optarg) / 100.0;
+            if (resize_rate > 1.0) {
+                resize_rate = 1.0;
+            }
+            break;
+        case 'u':
+            update_rate = atof(optarg) / 100.0;
+            if (update_rate > 1.0) {
+                update_rate = 1.0;
+            }
+            break;
+        }
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    parse_args(argc, argv);
+    htable_init();
+    create_threads();
+    run_test();
+    pr_stats();
+    return 0;
+}