| Message ID | 20200626200950.1015121-2-richard.henderson@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | tests/qht-bench: Adjust rate/threshold computation | expand |
On 6/26/20 10:09 PM, Richard Henderson wrote: > Since the seed must be non-zero, subtracting 1 means puts the > rate in 0..UINT64_MAX-1, which allows the 0 and UINT64_MAX > thresholds to corrspond to 0% (never) and 100% (always). > > Suggested-by: Emilio G. Cota <cota@braap.org> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > tests/qht-bench.c | 22 +++++++++++++++------- > 1 file changed, 15 insertions(+), 7 deletions(-) > > diff --git a/tests/qht-bench.c b/tests/qht-bench.c > index eb88a90137..ad885d89d0 100644 > --- a/tests/qht-bench.c > +++ b/tests/qht-bench.c > @@ -25,7 +25,13 @@ struct thread_stats { > struct thread_info { > void (*func)(struct thread_info *); > struct thread_stats stats; > - uint64_t r; > + /* > + * Seed is in the range [1..UINT64_MAX], because the RNG requires > + * a non-zero seed. To use, subtract 1 and compare against the > + * threshold with </>=. This lets threshold = 0 never match (0% hit), > + * and threshold = UINT64_MAX always match (100% hit). > + */ > + uint64_t seed; > bool write_op; /* writes alternate between insertions and removals */ > bool resize_down; > } QEMU_ALIGNED(64); /* avoid false sharing among threads */ > @@ -131,8 +137,9 @@ static uint64_t xorshift64star(uint64_t x) > static void do_rz(struct thread_info *info) > { > struct thread_stats *stats = &info->stats; > + uint64_t r = info->seed - 1; > > - if (info->r < resize_threshold) { > + if (r < resize_threshold) { > size_t size = info->resize_down ? resize_min : resize_max; > bool resized; > > @@ -151,13 +158,14 @@ static void do_rz(struct thread_info *info) > static void do_rw(struct thread_info *info) > { > struct thread_stats *stats = &info->stats; > + uint64_t r = info->seed - 1; > uint32_t hash; > long *p; > > - if (info->r >= update_threshold) { > + if (r >= update_threshold) { > bool read; > > - p = &keys[info->r & (lookup_range - 1)]; > + p = &keys[r & (lookup_range - 1)]; > hash = hfunc(*p); > read = qht_lookup(&ht, p, hash); > if (read) { > @@ -166,7 +174,7 @@ static void do_rw(struct thread_info *info) > stats->not_rd++; > } > } else { > - p = &keys[info->r & (update_range - 1)]; > + p = &keys[r & (update_range - 1)]; > hash = hfunc(*p); > if (info->write_op) { > bool written = false; > @@ -208,7 +216,7 @@ static void *thread_func(void *p) > > rcu_read_lock(); > while (!atomic_read(&test_stop)) { > - info->r = xorshift64star(info->r); > + info->seed = xorshift64star(info->seed); > info->func(info); > } > rcu_read_unlock(); > @@ -221,7 +229,7 @@ static void *thread_func(void *p) > 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); > + info->seed = (i + 1) ^ time(NULL); > /* the first update will be a write */ > info->write_op = true; > /* the first resize will be down */ > Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
diff --git a/tests/qht-bench.c b/tests/qht-bench.c index eb88a90137..ad885d89d0 100644 --- a/tests/qht-bench.c +++ b/tests/qht-bench.c @@ -25,7 +25,13 @@ struct thread_stats { struct thread_info { void (*func)(struct thread_info *); struct thread_stats stats; - uint64_t r; + /* + * Seed is in the range [1..UINT64_MAX], because the RNG requires + * a non-zero seed. To use, subtract 1 and compare against the + * threshold with </>=. This lets threshold = 0 never match (0% hit), + * and threshold = UINT64_MAX always match (100% hit). + */ + uint64_t seed; bool write_op; /* writes alternate between insertions and removals */ bool resize_down; } QEMU_ALIGNED(64); /* avoid false sharing among threads */ @@ -131,8 +137,9 @@ static uint64_t xorshift64star(uint64_t x) static void do_rz(struct thread_info *info) { struct thread_stats *stats = &info->stats; + uint64_t r = info->seed - 1; - if (info->r < resize_threshold) { + if (r < resize_threshold) { size_t size = info->resize_down ? resize_min : resize_max; bool resized; @@ -151,13 +158,14 @@ static void do_rz(struct thread_info *info) static void do_rw(struct thread_info *info) { struct thread_stats *stats = &info->stats; + uint64_t r = info->seed - 1; uint32_t hash; long *p; - if (info->r >= update_threshold) { + if (r >= update_threshold) { bool read; - p = &keys[info->r & (lookup_range - 1)]; + p = &keys[r & (lookup_range - 1)]; hash = hfunc(*p); read = qht_lookup(&ht, p, hash); if (read) { @@ -166,7 +174,7 @@ static void do_rw(struct thread_info *info) stats->not_rd++; } } else { - p = &keys[info->r & (update_range - 1)]; + p = &keys[r & (update_range - 1)]; hash = hfunc(*p); if (info->write_op) { bool written = false; @@ -208,7 +216,7 @@ static void *thread_func(void *p) rcu_read_lock(); while (!atomic_read(&test_stop)) { - info->r = xorshift64star(info->r); + info->seed = xorshift64star(info->seed); info->func(info); } rcu_read_unlock(); @@ -221,7 +229,7 @@ static void *thread_func(void *p) 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); + info->seed = (i + 1) ^ time(NULL); /* the first update will be a write */ info->write_op = true; /* the first resize will be down */
Since the seed must be non-zero, subtracting 1 means puts the rate in 0..UINT64_MAX-1, which allows the 0 and UINT64_MAX thresholds to corrspond to 0% (never) and 100% (always). Suggested-by: Emilio G. Cota <cota@braap.org> Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- tests/qht-bench.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) -- 2.25.1