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Date:      Fri, 25 Nov 2016 13:49:33 +0000 (UTC)
From:      Fabien Thomas <fabient@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r309143 - head/sys/libkern
Message-ID:  <201611251349.uAPDnX09042110@repo.freebsd.org>
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Author: fabient
Date: Fri Nov 25 13:49:33 2016
New Revision: 309143
URL: https://svnweb.freebsd.org/changeset/base/309143

Log:
  In a dual processor system (2*6 cores) during IPSec throughput tests,
  we see a lot of contention on the arc4 lock, used to generate the IV
  of the ESP output packets.
  
  The idea of this patch is to split this mutex in order to reduce the
  contention on this lock.
  
  Reviewed by:	delphij, markm, ache
  Approved by:	so
  Obtained from: emeric.poupon@stormshield.eu
  MFC after: 1 month
  Sponsored by:	Stormshield
  Differential Revision:	https://reviews.freebsd.org/D8130

Modified:
  head/sys/libkern/arc4random.c

Modified: head/sys/libkern/arc4random.c
==============================================================================
--- head/sys/libkern/arc4random.c	Fri Nov 25 13:15:28 2016	(r309142)
+++ head/sys/libkern/arc4random.c	Fri Nov 25 13:49:33 2016	(r309143)
@@ -19,6 +19,8 @@ __FBSDID("$FreeBSD$");
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/time.h>
+#include <sys/smp.h>
+#include <sys/malloc.h>
 
 #define	ARC4_RESEED_BYTES 65536
 #define	ARC4_RESEED_SECONDS 300
@@ -26,13 +28,23 @@ __FBSDID("$FreeBSD$");
 
 int arc4rand_iniseed_state = ARC4_ENTR_NONE;
 
-static u_int8_t arc4_i, arc4_j;
-static int arc4_numruns = 0;
-static u_int8_t arc4_sbox[256];
-static time_t arc4_t_reseed;
-static struct mtx arc4_mtx;
+MALLOC_DEFINE(M_ARC4RANDOM, "arc4random", "arc4random structures");
 
-static u_int8_t arc4_randbyte(void);
+struct arc4_s {
+	u_int8_t i, j;
+	int numruns;
+	u_int8_t sbox[256];
+	time_t t_reseed;
+
+	struct mtx mtx;
+};
+
+static struct arc4_s *arc4inst = NULL;
+
+#define ARC4_FOREACH(_arc4) \
+	for (_arc4 = &arc4inst[0]; _arc4 <= &arc4inst[mp_maxid]; _arc4++)
+
+static u_int8_t arc4_randbyte(struct arc4_s *arc4);
 
 static __inline void
 arc4_swap(u_int8_t *a, u_int8_t *b)
@@ -48,7 +60,7 @@ arc4_swap(u_int8_t *a, u_int8_t *b)
  * Stir our S-box.
  */
 static void
-arc4_randomstir(void)
+arc4_randomstir(struct arc4_s* arc4)
 {
 	u_int8_t key[ARC4_KEYBYTES];
 	int n;
@@ -60,15 +72,15 @@ arc4_randomstir(void)
 	 */
 	(void)read_random(key, ARC4_KEYBYTES);
 	getmicrouptime(&tv_now);
-	mtx_lock(&arc4_mtx);
+	mtx_lock(&arc4->mtx);
 	for (n = 0; n < 256; n++) {
-		arc4_j = (arc4_j + arc4_sbox[n] + key[n]) % 256;
-		arc4_swap(&arc4_sbox[n], &arc4_sbox[arc4_j]);
+		arc4->j = (arc4->j + arc4->sbox[n] + key[n]) % 256;
+		arc4_swap(&arc4->sbox[n], &arc4->sbox[arc4->j]);
 	}
-	arc4_i = arc4_j = 0;
+	arc4->i = arc4->j = 0;
 	/* Reset for next reseed cycle. */
-	arc4_t_reseed = tv_now.tv_sec + ARC4_RESEED_SECONDS;
-	arc4_numruns = 0;
+	arc4->t_reseed = tv_now.tv_sec + ARC4_RESEED_SECONDS;
+	arc4->numruns = 0;
 	/*
 	 * Throw away the first N words of output, as suggested in the
 	 * paper "Weaknesses in the Key Scheduling Algorithm of RC4"
@@ -77,8 +89,9 @@ arc4_randomstir(void)
 	 * http://dl.acm.org/citation.cfm?id=646557.694759
 	 */
 	for (n = 0; n < 256*4; n++)
-		arc4_randbyte();
-	mtx_unlock(&arc4_mtx);
+		arc4_randbyte(arc4);
+
+	mtx_unlock(&arc4->mtx);
 }
 
 /*
@@ -87,33 +100,57 @@ arc4_randomstir(void)
 static void
 arc4_init(void)
 {
+	struct arc4_s *arc4;
 	int n;
 
-	mtx_init(&arc4_mtx, "arc4_mtx", NULL, MTX_DEF);
-	arc4_i = arc4_j = 0;
-	for (n = 0; n < 256; n++)
-		arc4_sbox[n] = (u_int8_t) n;
+	arc4inst = malloc((mp_maxid + 1) * sizeof(struct arc4_s),
+			M_ARC4RANDOM, M_NOWAIT | M_ZERO);
+	KASSERT(arc4inst != NULL, ("arc4_init: memory allocation error"));
+
+	ARC4_FOREACH(arc4) {
+		mtx_init(&arc4->mtx, "arc4_mtx", NULL, MTX_DEF);
+
+		arc4->i = arc4->j = 0;
+		for (n = 0; n < 256; n++)
+			arc4->sbox[n] = (u_int8_t) n;
 
-	arc4_t_reseed = 0;
+		arc4->t_reseed = -1;
+		arc4->numruns = 0;
+	}
 }
+SYSINIT(arc4, SI_SUB_LOCK, SI_ORDER_ANY, arc4_init, NULL);
+
+
+static void
+arc4_uninit(void)
+{
+	struct arc4_s *arc4;
+
+	ARC4_FOREACH(arc4) {
+		mtx_destroy(&arc4->mtx);
+	}
+
+	free(arc4inst, M_ARC4RANDOM);
+}
+
+SYSUNINIT(arc4, SI_SUB_LOCK, SI_ORDER_ANY, arc4_uninit, NULL);
 
-SYSINIT(arc4_init, SI_SUB_LOCK, SI_ORDER_ANY, arc4_init, NULL);
 
 /*
  * Generate a random byte.
  */
 static u_int8_t
-arc4_randbyte(void)
+arc4_randbyte(struct arc4_s *arc4)
 {
 	u_int8_t arc4_t;
 
-	arc4_i = (arc4_i + 1) % 256;
-	arc4_j = (arc4_j + arc4_sbox[arc4_i]) % 256;
+	arc4->i = (arc4->i + 1) % 256;
+	arc4->j = (arc4->j + arc4->sbox[arc4->i]) % 256;
 
-	arc4_swap(&arc4_sbox[arc4_i], &arc4_sbox[arc4_j]);
+	arc4_swap(&arc4->sbox[arc4->i], &arc4->sbox[arc4->j]);
 
-	arc4_t = (arc4_sbox[arc4_i] + arc4_sbox[arc4_j]) % 256;
-	return arc4_sbox[arc4_t];
+	arc4_t = (arc4->sbox[arc4->i] + arc4->sbox[arc4->j]) % 256;
+	return arc4->sbox[arc4_t];
 }
 
 /*
@@ -124,20 +161,26 @@ arc4rand(void *ptr, u_int len, int resee
 {
 	u_char *p;
 	struct timeval tv;
+	struct arc4_s *arc4;
+
+	if (reseed || atomic_cmpset_int(&arc4rand_iniseed_state,
+			ARC4_ENTR_HAVE, ARC4_ENTR_SEED)) {
+		ARC4_FOREACH(arc4)
+			arc4_randomstir(arc4);
+	}
 
+	arc4 = &arc4inst[curcpu];
 	getmicrouptime(&tv);
-	if (atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE,
-	    ARC4_ENTR_SEED) || reseed ||
-	   (arc4_numruns > ARC4_RESEED_BYTES) ||
-	   (tv.tv_sec > arc4_t_reseed))
-		arc4_randomstir();
+	if ((arc4->numruns > ARC4_RESEED_BYTES) ||
+		(tv.tv_sec > arc4->t_reseed))
+		arc4_randomstir(arc4);
 
-	mtx_lock(&arc4_mtx);
-	arc4_numruns += len;
+	mtx_lock(&arc4->mtx);
+	arc4->numruns += len;
 	p = ptr;
 	while (len--)
-		*p++ = arc4_randbyte();
-	mtx_unlock(&arc4_mtx);
+		*p++ = arc4_randbyte(arc4);
+	mtx_unlock(&arc4->mtx);
 }
 
 uint32_t

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