Currently, we use the jiffies counter as a time source, by staring at
it until a HZ period elapses, and then staring at it again and perform
as many XOR operations as we can at the same time until another HZ
period elapses, so that we can calculate the throughput. This takes
longer than necessary, and depends on HZ, which is undesirable, since
HZ is system dependent.
Let's use the ktime interface instead, and use it to time a fixed
number of XOR operations, which can be done much faster, and makes
the time spent depend on the performance level of the system itself,
which is much more reasonable.
On ThunderX2, I get the following results:
Before:
[72625.956765] xor: measuring software checksum speed
[72625.993104] 8regs : 10169.000 MB/sec
[72626.033099] 32regs : 12050.000 MB/sec
[72626.073095] arm64_neon: 11100.000 MB/sec
[72626.073097] xor: using function: 32regs (12050.000 MB/sec)
After:
[ 2503.189696] xor: measuring software checksum speed
[ 2503.189896] 8regs : 10556 MB/sec
[ 2503.190061] 32regs : 12538 MB/sec
[ 2503.190250] arm64_neon : 11470 MB/sec
[ 2503.190252] xor: using function: 32regs (12538 MB/sec)
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
crypto/xor.c | 36 ++++++++------------
1 file changed, 15 insertions(+), 21 deletions(-)
diff --git a/crypto/xor.c b/crypto/xor.c
index b42c38343733..23f98b451b69 100644
--- a/crypto/xor.c
+++ b/crypto/xor.c
@@ -76,49 +76,43 @@ static int __init register_xor_blocks(void)
}
#endif
-#define BENCH_SIZE (PAGE_SIZE)
+#define BENCH_SIZE 4096
+#define REPS 100
static void __init
do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
{
int speed;
- unsigned long now, j;
- int i, count, max;
+ int i, j, count;
+ ktime_t min, start, diff;
tmpl->next = template_list;
template_list = tmpl;
preempt_disable();
- /*
- * Count the number of XORs done during a whole jiffy, and use
- * this to calculate the speed of checksumming. We use a 2-page
- * allocation to have guaranteed color L1-cache layout.
- */
- max = 0;
+ min = (ktime_t)S64_MAX;
for (i = 0; i < 5; i++) {
- j = jiffies;
- count = 0;
- while ((now = jiffies) == j)
- cpu_relax();
- while (time_before(jiffies, now + 1)) {
+ start = ktime_get();
+ for (j = 0; j < REPS; j++) {
mb(); /* prevent loop optimzation */
tmpl->do_2(BENCH_SIZE, b1, b2);
mb();
count++;
mb();
}
- if (count > max)
- max = count;
+ diff = ktime_sub(ktime_get(), start);
+ if (diff < min)
+ min = diff;
}
preempt_enable();
- speed = max * (HZ * BENCH_SIZE / 1024);
+ // bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
+ speed = (1000 * REPS * BENCH_SIZE) / (u32)min;
tmpl->speed = speed;
- printk(KERN_INFO " %-10s: %5d.%03d MB/sec\n", tmpl->name,
- speed / 1000, speed % 1000);
+ printk(KERN_INFO " %-16s: %5d MB/sec\n", tmpl->name, speed);
}
static int __init
@@ -158,8 +152,8 @@ calibrate_xor_blocks(void)
if (f->speed > fastest->speed)
fastest = f;
- printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
- fastest->name, fastest->speed / 1000, fastest->speed % 1000);
+ printk(KERN_INFO "xor: using function: %s (%d MB/sec)\n",
+ fastest->name, fastest->speed);
#undef xor_speed
--
2.17.1
