Hi George,
On top of the above patch, I applied the following to add 64-bit pool
support. I had to use a union to avoid type punning warnings.
When building a 64-bit kernel and running under under KVM, I'm finding
that the 64-bit mix function which you suggested is twice as slow.
Using the (new) 32-bit function:
31821 23970
31629 24366
30856 24182
Using the 64-bit mixing function:
60438 44369
60820 45402
58778 45419
- Ted
diff --git a/drivers/char/random.c b/drivers/char/random.c
index b19edad..0685413 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -257,6 +257,7 @@
#include <linux/kmemcheck.h>
#include <linux/workqueue.h>
#include <linux/irq.h>
+#include <linux/bitops.h>
#include <asm/processor.h>
#include <asm/uaccess.h>
@@ -267,7 +268,8 @@
#define CREATE_TRACE_POINTS
#include <trace/events/random.h>
-/* #define ADD_INTERRUPT_BENCH */
+#define ADD_INTERRUPT_BENCH
+/* #define FORCE_32_VERSION */
/*
* Configuration information
@@ -548,7 +550,10 @@ static void mix_pool_bytes(struct entropy_store *r, const
void *in,
}
struct fast_pool {
- __u32 pool[4];
+ union {
+ __u32 pool32[4];
+ __u64 pool64[2];
+ } pool;
unsigned long last;
unsigned char count;
unsigned char notimer_count;
@@ -560,10 +565,32 @@ struct fast_pool {
* collector. It's hardcoded for an 128 bit pool and assumes that any
* locks that might be needed are taken by the caller.
*/
+#if (BITS_PER_LONG == 64) && !defined(FORCE_32_VERSION)
+#warning Building 64 bit fast_mix
static void fast_mix(struct fast_pool *f)
{
- __u32 a = f->pool[0], b = f->pool[1];
- __u32 c = f->pool[2], d = f->pool[3];
+ __u64 a = f->pool.pool64[0], b = f->pool.pool64[1];
+
+ a += b; b = rol64(b, 52);
+ b ^= a; a = rol64(a, 10);
+ a += b; b = rol64(b, 47);
+ b ^= a; a = rol64(a, 17);
+
+ a += b; b = rol64(b, 52);
+ b ^= a; a = rol64(a, 10);
+ a += b; b = rol64(b, 47);
+ b ^= a; a = rol64(a, 17);
+
+ f->pool.pool64[0] = a; f->pool.pool64[1] = b;
+ f->count++;
+}
+
+#else
+#warning Building 32 bit fast_mix
+static void fast_mix(struct fast_pool *f)
+{
+ __u32 a = f->pool.pool32[0], b = f->pool.pool32[1];
+ __u32 c = f->pool.pool32[2], d = f->pool.pool32[3];
a += b; c += d;
b = rol32(a, 6); d = rol32(c, 27);
@@ -581,10 +608,11 @@ static void fast_mix(struct fast_pool *f)
b = rol32(a, 16); d = rol32(c, 14);
d ^= a; b ^= c;
- f->pool[0] = a; f->pool[1] = b;
- f->pool[2] = c; f->pool[3] = d;
+ f->pool.pool32[0] = a; f->pool.pool32[1] = b;
+ f->pool.pool32[2] = c; f->pool.pool32[3] = d;
f->count++;
}
+#endif
/*
* Credit (or debit) the entropy store with n bits of entropy.
@@ -870,11 +898,11 @@ void add_interrupt_randomness(int irq, int irq_flags)
c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
j_high = (sizeof(now) > 4) ? now >> 32 : 0;
- fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
- fast_pool->pool[1] ^= now ^ c_high;
+ fast_pool->pool.pool32[0] ^= cycles ^ j_high ^ irq;
+ fast_pool->pool.pool32[1] ^= now ^ c_high;
ip = regs ? instruction_pointer(regs) : _RET_IP_;
- fast_pool->pool[2] ^= ip;
- fast_pool->pool[3] ^= ip >> 32;
+ fast_pool->pool.pool32[2] ^= ip;
+ fast_pool->pool.pool32[3] ^= ip >> 32;
fast_mix(fast_pool);
if ((irq_flags & __IRQF_TIMER) == 0)
--
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