From: Anton Blanchard <anton@samba.org>
I tested how long it took to do a dd from /dev/random on ppc64 before and
after this patch, while doing a ping flood from another machine.
before:
# /usr/bin/time dd if=/dev/random of=/dev/zero count=1k
0+51 records in
Command terminated by signal 2
0.00user 0.00system 19:18.46elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
I gave up after 19 minutes.
after:
# /usr/bin/time dd if=/dev/random of=/dev/zero count=1k
0+1024 records in
0.00user 0.00system 0:33.38elapsed 0%CPU (0avgtext+0avgdata 0maxresident)k
Just over 33 seconds. Better.
From: Arnd Bergmann <arnd@arndb.de>
I noticed that only i386 and x86-64 are currently using a high resolution
timer source when adding randomness. Since many architectures have a
working get_cycles() implementation, it seems rather straightforward to use
that.
Has this been discussed before, or can anyone comment on the implementation
below?
This patch attempts to take into account the size of cycles_t, which is
either 32 or 64 bits wide but independent of the architecture's word size.
The behavior should be nearly identical to the old one on i386, x86-64 and
all architectures without a time stamp counter, while finding more entropy
on the other architectures.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/drivers/char/random.c | 31 ++++++++++++-------------------
25-akpm/include/asm-i386/timex.h | 13 ++++++++-----
2 files changed, 20 insertions(+), 24 deletions(-)
diff -puN drivers/char/random.c~using-get_cycles-for-add_timer_randomness drivers/char/random.c
--- 25/drivers/char/random.c~using-get_cycles-for-add_timer_randomness 2004-08-15 15:45:13.514016424 -0700
+++ 25-akpm/drivers/char/random.c 2004-08-15 15:46:14.773703536 -0700
@@ -781,8 +781,8 @@ static void batch_entropy_process(void *
/* There is one of these per entropy source */
struct timer_rand_state {
- __u32 last_time;
- __s32 last_delta,last_delta2;
+ cycles_t last_time;
+ long last_delta,last_delta2;
int dont_count_entropy:1;
};
@@ -799,14 +799,12 @@ static struct timer_rand_state *irq_time
* The number "num" is also added to the pool - it should somehow describe
* the type of event which just happened. This is currently 0-255 for
* keyboard scan codes, and 256 upwards for interrupts.
- * On the i386, this is assumed to be at most 16 bits, and the high bits
- * are used for a high-resolution timer.
*
*/
static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
{
- __u32 time;
- __s32 delta, delta2, delta3;
+ cycles_t time;
+ long delta, delta2, delta3;
int entropy = 0;
/* if over the trickle threshold, use only 1 in 4096 samples */
@@ -814,22 +812,17 @@ static void add_timer_randomness(struct
(__get_cpu_var(trickle_count)++ & 0xfff))
return;
-#if defined (__i386__) || defined (__x86_64__)
- if (cpu_has_tsc) {
- __u32 high;
- rdtsc(time, high);
- num ^= high;
+ /*
+ * Use get_cycles() if implemented, otherwise fall back to
+ * jiffies.
+ */
+ time = get_cycles();
+ if (time != 0) {
+ if (sizeof(time) > 4)
+ num ^= (u32)(time >> 32);
} else {
time = jiffies;
}
-#elif defined (__sparc_v9__)
- unsigned long tick = tick_ops->get_tick();
-
- time = (unsigned int) tick;
- num ^= (tick >> 32UL);
-#else
- time = jiffies;
-#endif
/*
* Calculate number of bits of randomness we probably added.
diff -puN include/asm-i386/timex.h~using-get_cycles-for-add_timer_randomness include/asm-i386/timex.h
--- 25/include/asm-i386/timex.h~using-get_cycles-for-add_timer_randomness 2004-08-15 15:45:13.516016120 -0700
+++ 25-akpm/include/asm-i386/timex.h 2004-08-15 15:45:13.522015208 -0700
@@ -7,7 +7,7 @@
#define _ASMi386_TIMEX_H
#include <linux/config.h>
-#include <asm/msr.h>
+#include <asm/processor.h>
#ifdef CONFIG_X86_ELAN
# define CLOCK_TICK_RATE 1189200 /* AMD Elan has different frequency! */
@@ -40,14 +40,17 @@ extern cycles_t cacheflush_time;
static inline cycles_t get_cycles (void)
{
+ unsigned long long ret=0;
+
#ifndef CONFIG_X86_TSC
- return 0;
-#else
- unsigned long long ret;
+ if (!cpu_has_tsc)
+ return 0;
+#endif
+#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
rdtscll(ret);
- return ret;
#endif
+ return ret;
}
extern unsigned long cpu_khz;
_