From: "Theodore Ts'o" <tytso@mit.edu>
To: Linux Kernel Developers List <linux-kernel@vger.kernel.org>
Cc: hpa@zytor.com, joern@logfs.org, macro@linux-mips.org,
ralf@linux-mips.org, dave.taht@gmail.com, blogic@openwrt.org,
andrewmcgr@gmail.com, smueller@chronox.de, geert@linux-m68k.org,
tg@mirbsd.de, "Theodore Ts'o" <tytso@mit.edu>
Subject: [PATCH, RFC 11/12] random: speed up the fast_mix function by a factor of four
Date: Sun, 22 Sep 2013 16:38:57 -0400 [thread overview]
Message-ID: <1379882338-7209-12-git-send-email-tytso@mit.edu> (raw)
In-Reply-To: <1379882338-7209-1-git-send-email-tytso@mit.edu>
By mixing the entropy in chunks of 32-bit words instead of byte by
byte, we can speed up the fast_mix function significantly. Since it
is called on every single interrupt, on systems with a very heavy
interrupt load, this can make a noticeable different.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: Jörn Engel <joern@logfs.org>
---
drivers/char/random.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 3439b1c..86879d1 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -583,21 +583,26 @@ 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.
*/
-static void fast_mix(struct fast_pool *f, const void *in, int nbytes)
+static void fast_mix(struct fast_pool *f, __u32 input[4])
{
- const char *bytes = in;
__u32 w;
- unsigned i = f->count;
unsigned input_rotate = f->rotate;
- while (nbytes--) {
- w = rol32(*bytes++, input_rotate & 31) ^ f->pool[i & 3] ^
- f->pool[(i + 1) & 3];
- f->pool[i & 3] = (w >> 3) ^ twist_table[w & 7];
- input_rotate += (i++ & 3) ? 7 : 14;
- }
- f->count = i;
+ w = rol32(input[0], input_rotate) ^ f->pool[0] ^ f->pool[3];
+ f->pool[0] = (w >> 3) ^ twist_table[w & 7];
+ input_rotate = (input_rotate + 14) & 31;
+ w = rol32(input[1], input_rotate) ^ f->pool[1] ^ f->pool[0];
+ f->pool[1] = (w >> 3) ^ twist_table[w & 7];
+ input_rotate = (input_rotate + 7) & 31;
+ w = rol32(input[2], input_rotate) ^ f->pool[2] ^ f->pool[1];
+ f->pool[2] = (w >> 3) ^ twist_table[w & 7];
+ input_rotate = (input_rotate + 7) & 31;
+ w = rol32(input[3], input_rotate) ^ f->pool[3] ^ f->pool[2];
+ f->pool[3] = (w >> 3) ^ twist_table[w & 7];
+ input_rotate = (input_rotate + 7) & 31;
+
f->rotate = input_rotate;
+ f->count++;
}
/*
@@ -836,10 +841,9 @@ void add_interrupt_randomness(int irq, int irq_flags)
input[3] = ip >> 32;
}
- fast_mix(fast_pool, input, sizeof(input));
+ fast_mix(fast_pool, input);
- if ((fast_pool->count & 1023) &&
- !time_after(now, fast_pool->last + HZ))
+ if ((fast_pool->count & 63) && !time_after(now, fast_pool->last + HZ))
return;
fast_pool->last = now;
--
1.7.12.rc0.22.gcdd159b
next prev parent reply other threads:[~2013-09-22 20:40 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-22 20:38 [PATCH, RFC 00/12] random driver changes Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 01/12] random: run random_int_secret_init() run after all late_initcalls Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 02/12] random: Statically compute poolbitshift, poolbytes, poolbits Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 03/12] random: Allow fractional bits to be tracked Theodore Ts'o
2013-09-23 4:01 ` Theodore Ts'o
2013-09-23 4:03 ` H. Peter Anvin
2013-09-22 20:38 ` [PATCH, RFC 04/12] random: Account for entropy loss due to overwrites Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 05/12] random: fix the tracepoint for get_random_bytes(_arch) Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 06/12] random: optimize spinlock use in add_device_randomness() Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 07/12] random: allow architectures to optionally define random_get_entropy() Theodore Ts'o
2013-09-23 10:38 ` Stephan Mueller
2013-09-23 11:05 ` Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 08/12] random: mix in architectural randomness earlier in extract_buf() Theodore Ts'o
2013-09-23 4:11 ` H. Peter Anvin
2013-09-23 4:33 ` Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 09/12] random: optimize the entropy_store structure Theodore Ts'o
2013-09-22 20:38 ` [PATCH, RFC 10/12] random: cap the rate which the /dev/urandom pool gets reseeded Theodore Ts'o
2013-09-22 21:21 ` H. Peter Anvin
2013-09-22 21:40 ` Theodore Ts'o
2013-09-22 22:45 ` H. Peter Anvin
2013-09-22 23:23 ` Theodore Ts'o
2013-09-23 0:26 ` H. Peter Anvin
2013-09-22 20:38 ` Theodore Ts'o [this message]
2013-09-22 20:38 ` [PATCH, RFC 12/12] random: adjust the generator polynomials in the mixing function slightly Theodore Ts'o
2013-09-25 10:51 ` Jörg-Volker Peetz
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