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* [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
@ 2015-03-17 16:18 Robert Sanford
  2015-03-27 16:38 ` Sanford, Robert
  0 siblings, 1 reply; 9+ messages in thread
From: Robert Sanford @ 2015-03-17 16:18 UTC (permalink / raw)
  To: David.Marchand, Bruce.Richardson, dev

The implementation of rte_rand() returns only 62 bits of 
pseudo-randomness, because the underlying calls to lrand48()
"return non-negative long integers uniformly distributed
between 0 and 2^31."

We have written a potential fix, but before we spend more
time testing and refining it, I wanted to check with you
guys.

We switched to using the reentrant versions of [ls]rand48,
and maintain per-lcore state. We need ~2.06 calls to
lrand48_r(), per call to rte_rand().

Do you agree with the approach we've taken in this patch?


Thanks,
Robert

---
 lib/librte_eal/common/include/rte_random.h |   33 +++++++++++++++++++++++++--
 lib/librte_eal/linuxapp/eal/eal_thread.c   |    7 ++++++
 2 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/lib/librte_eal/common/include/rte_random.h b/lib/librte_eal/common/include/rte_random.h
index 24ae836..b9248cd 100644
--- a/lib/librte_eal/common/include/rte_random.h
+++ b/lib/librte_eal/common/include/rte_random.h
@@ -46,6 +46,17 @@ extern "C" {
 
 #include <stdint.h>
 #include <stdlib.h>
+#include <rte_per_lcore.h>
+#include <rte_branch_prediction.h>
+
+struct rte_rand_data {
+	struct drand48_data _dr48;
+	uint32_t _hi_bits;
+	uint8_t _bits_left;
+};
+
+RTE_DECLARE_PER_LCORE(struct rte_rand_data, _rand_data);
+
 
 /**
  * Seed the pseudo-random generator.
@@ -60,7 +71,7 @@ extern "C" {
 static inline void
 rte_srand(uint64_t seedval)
 {
-	srand48((long unsigned int)seedval);
+	srand48_r((long unsigned int)seedval, &RTE_PER_LCORE(_rand_data)._dr48);
 }
 
 /**
@@ -76,10 +87,26 @@ rte_srand(uint64_t seedval)
 static inline uint64_t
 rte_rand(void)
 {
+	struct rte_rand_data *rd = &RTE_PER_LCORE(_rand_data);
 	uint64_t val;
-	val = lrand48();
+	uint32_t hi_bits;
+	long int result;
+
+	if (unlikely(rd->_bits_left < 2)) {
+		lrand48_r(&rd->_dr48, &result);
+		rd->_hi_bits |= (uint32_t)result << (1 - rd->_bits_left);
+		rd->_bits_left += 31;
+	}
+
+	hi_bits = rd->_hi_bits;
+	lrand48_r(&rd->_dr48, &result);
+	val = (uint32_t)result | (hi_bits & 0x8000000);
 	val <<= 32;
-	val += lrand48();
+	hi_bits <<= 1;
+	lrand48_r(&rd->_dr48, &result);
+	val |= (uint32_t)result | (hi_bits & 0x8000000);
+	rd->_hi_bits = hi_bits << 1;
+	rd->_bits_left -= 2;
 	return val;
 }
 
diff --git a/lib/librte_eal/linuxapp/eal/eal_thread.c b/lib/librte_eal/linuxapp/eal/eal_thread.c
index 5635c7d..08e7f72 100644
--- a/lib/librte_eal/linuxapp/eal/eal_thread.c
+++ b/lib/librte_eal/linuxapp/eal/eal_thread.c
@@ -52,6 +52,8 @@
 #include <rte_eal.h>
 #include <rte_per_lcore.h>
 #include <rte_lcore.h>
+#include <rte_cycles.h>
+#include <rte_random.h>
 
 #include "eal_private.h"
 #include "eal_thread.h"
@@ -59,6 +61,8 @@
 RTE_DEFINE_PER_LCORE(unsigned, _lcore_id) = LCORE_ID_ANY;
 RTE_DEFINE_PER_LCORE(unsigned, _socket_id) = (unsigned)SOCKET_ID_ANY;
 RTE_DEFINE_PER_LCORE(rte_cpuset_t, _cpuset);
+RTE_DEFINE_PER_LCORE(struct rte_rand_data, _rand_data);
+
 
 /*
  * Send a message to a slave lcore identified by slave_id to call a
@@ -147,6 +151,9 @@ eal_thread_loop(__attribute__((unused)) void *arg)
 	/* set the lcore ID in per-lcore memory area */
 	RTE_PER_LCORE(_lcore_id) = lcore_id;
 
+	/* seed per-lcore PRNG */
+	rte_srand(rte_rdtsc());
+
 	/* set CPU affinity */
 	if (eal_thread_set_affinity() < 0)
 		rte_panic("cannot set affinity\n");
-- 
1.7.1

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
  2015-03-17 16:18 [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits Robert Sanford
@ 2015-03-27 16:38 ` Sanford, Robert
  2015-03-28  0:02   ` Stephen Hemminger
  2015-03-28  0:03   ` Stephen Hemminger
  0 siblings, 2 replies; 9+ messages in thread
From: Sanford, Robert @ 2015-03-27 16:38 UTC (permalink / raw)
  To: dev, David.Marchand, Bruce.Richardson

Never mind ... I cancel the previous suggestion. After further reading on
RNGs, I believe we should abandon the use of lrand48() and implement our
own RNG based on the so-called KISS family of RNGs originally proposed by
the late George Marsaglia. In his excellent paper, "Good Practice in
(Pseudo) Random Number Generation for Bioinformatics Applications", David
Jones (UCL Bioinformatics Group) describes a few variants of KISS
generators. This paper, and Robert G. Brown's (Duke Univ.) comprehensive
"Dieharder" random number test suite work show that KISS RNGs are simple
and fast, yet high quality.

Something like JLKISS64(), with state kept in TLS, would be ideal for DPDK
use. In limited experiments, I found JLKISS64() (not inlined, compiles to
~40 instructions) to be ~4 times faster than rte_rand(). This is probably
because JLKISS64() achieves integer-instruction parallelism, while
rte_rand(), with its two calls to lrand48(), nrand48_r(), and
__drand48_iterate(), does not (and all those calls!).

Here is the JLKISS64() function, as it appears in Jones's GoodPracticeRNG
paper:

---

	
		
		
	
	
		
			
				
					/* Public domain code for JLKISS64 RNG - long period KISS RNG
producing 64-bit results */

					unsigned long long x = 123456789123ULL,y = 987654321987ULL; /* Seed
variables */
unsigned int z1 = 43219876, c1 = 6543217, z2 = 21987643, c2 = 1732654; /*
Seed variables */

					unsigned long long JLKISS64()
{

					    unsigned long long t;

					x = 1490024343005336237ULL * x + 123456789;
y ^= y << 21; y ^= y >> 17; y ^= y << 30; /* Do not set y=0! */
t = 4294584393ULL * z1 + c1; c1 = t >> 32; z1 = t;
t = 4246477509ULL * z2 + c2; c2 = t >> 32; z2 = t;

					return x + y + z1 + ((unsigned long long)z2 << 32); /* Return 64-bit
result */
}

				
			
		
	



--
Regards,
Robert



>The implementation of rte_rand() returns only 62 bits of
>pseudo-randomness, because the underlying calls to lrand48()
>"return non-negative long integers uniformly distributed
>between 0 and 2^31."
>
>We have written a potential fix, but before we spend more
>time testing and refining it, I wanted to check with you
>guys.
>
>We switched to using the reentrant versions of [ls]rand48,
>and maintain per-lcore state. We need ~2.06 calls to
>lrand48_r(), per call to rte_rand().
>
>Do you agree with the approach we've taken in this patch?
>
>
>Thanks,
>Robert
>
>---
> lib/librte_eal/common/include/rte_random.h |   33
>+++++++++++++++++++++++++--
> lib/librte_eal/linuxapp/eal/eal_thread.c   |    7 ++++++
> 2 files changed, 37 insertions(+), 3 deletions(-)
>
>diff --git a/lib/librte_eal/common/include/rte_random.h
>b/lib/librte_eal/common/include/rte_random.h
>index 24ae836..b9248cd 100644
>--- a/lib/librte_eal/common/include/rte_random.h
>+++ b/lib/librte_eal/common/include/rte_random.h
>@@ -46,6 +46,17 @@ extern "C" {
> 
> #include <stdint.h>
> #include <stdlib.h>
>+#include <rte_per_lcore.h>
>+#include <rte_branch_prediction.h>
>+
>+struct rte_rand_data {
>+	struct drand48_data _dr48;
>+	uint32_t _hi_bits;
>+	uint8_t _bits_left;
>+};
>+
>+RTE_DECLARE_PER_LCORE(struct rte_rand_data, _rand_data);
>+
> 
> /**
>  * Seed the pseudo-random generator.
>@@ -60,7 +71,7 @@ extern "C" {
> static inline void
> rte_srand(uint64_t seedval)
> {
>-	srand48((long unsigned int)seedval);
>+	srand48_r((long unsigned int)seedval, &RTE_PER_LCORE(_rand_data)._dr48);
> }
> 
> /**
>@@ -76,10 +87,26 @@ rte_srand(uint64_t seedval)
> static inline uint64_t
> rte_rand(void)
> {
>+	struct rte_rand_data *rd = &RTE_PER_LCORE(_rand_data);
> 	uint64_t val;
>-	val = lrand48();
>+	uint32_t hi_bits;
>+	long int result;
>+
>+	if (unlikely(rd->_bits_left < 2)) {
>+		lrand48_r(&rd->_dr48, &result);
>+		rd->_hi_bits |= (uint32_t)result << (1 - rd->_bits_left);
>+		rd->_bits_left += 31;
>+	}
>+
>+	hi_bits = rd->_hi_bits;
>+	lrand48_r(&rd->_dr48, &result);
>+	val = (uint32_t)result | (hi_bits & 0x8000000);
> 	val <<= 32;
>-	val += lrand48();
>+	hi_bits <<= 1;
>+	lrand48_r(&rd->_dr48, &result);
>+	val |= (uint32_t)result | (hi_bits & 0x8000000);
>+	rd->_hi_bits = hi_bits << 1;
>+	rd->_bits_left -= 2;
> 	return val;
> }
> 
>diff --git a/lib/librte_eal/linuxapp/eal/eal_thread.c
>b/lib/librte_eal/linuxapp/eal/eal_thread.c
>index 5635c7d..08e7f72 100644
>--- a/lib/librte_eal/linuxapp/eal/eal_thread.c
>+++ b/lib/librte_eal/linuxapp/eal/eal_thread.c
>@@ -52,6 +52,8 @@
> #include <rte_eal.h>
> #include <rte_per_lcore.h>
> #include <rte_lcore.h>
>+#include <rte_cycles.h>
>+#include <rte_random.h>
> 
> #include "eal_private.h"
> #include "eal_thread.h"
>@@ -59,6 +61,8 @@
> RTE_DEFINE_PER_LCORE(unsigned, _lcore_id) = LCORE_ID_ANY;
> RTE_DEFINE_PER_LCORE(unsigned, _socket_id) = (unsigned)SOCKET_ID_ANY;
> RTE_DEFINE_PER_LCORE(rte_cpuset_t, _cpuset);
>+RTE_DEFINE_PER_LCORE(struct rte_rand_data, _rand_data);
>+
> 
> /*
>  * Send a message to a slave lcore identified by slave_id to call a
>@@ -147,6 +151,9 @@ eal_thread_loop(__attribute__((unused)) void *arg)
> 	/* set the lcore ID in per-lcore memory area */
> 	RTE_PER_LCORE(_lcore_id) = lcore_id;
> 
>+	/* seed per-lcore PRNG */
>+	rte_srand(rte_rdtsc());
>+
> 	/* set CPU affinity */
> 	if (eal_thread_set_affinity() < 0)
> 		rte_panic("cannot set affinity\n");
>-- 
>1.7.1
>

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
  2015-03-27 16:38 ` Sanford, Robert
@ 2015-03-28  0:02   ` Stephen Hemminger
  2015-03-28  0:03   ` Stephen Hemminger
  1 sibling, 0 replies; 9+ messages in thread
From: Stephen Hemminger @ 2015-03-28  0:02 UTC (permalink / raw)
  To: Sanford, Robert; +Cc: dev

Please do this work upstream in glibc rather than in the corner case of
DPDK.


On Fri, Mar 27, 2015 at 9:38 AM, Sanford, Robert <rsanford@akamai.com>
wrote:

> Never mind ... I cancel the previous suggestion. After further reading on
> RNGs, I believe we should abandon the use of lrand48() and implement our
> own RNG based on the so-called KISS family of RNGs originally proposed by
> the late George Marsaglia. In his excellent paper, "Good Practice in
> (Pseudo) Random Number Generation for Bioinformatics Applications", David
> Jones (UCL Bioinformatics Group) describes a few variants of KISS
> generators. This paper, and Robert G. Brown's (Duke Univ.) comprehensive
> "Dieharder" random number test suite work show that KISS RNGs are simple
> and fast, yet high quality.
>
> Something like JLKISS64(), with state kept in TLS, would be ideal for DPDK
> use. In limited experiments, I found JLKISS64() (not inlined, compiles to
> ~40 instructions) to be ~4 times faster than rte_rand(). This is probably
> because JLKISS64() achieves integer-instruction parallelism, while
> rte_rand(), with its two calls to lrand48(), nrand48_r(), and
> __drand48_iterate(), does not (and all those calls!).
>
> Here is the JLKISS64() function, as it appears in Jones's GoodPracticeRNG
> paper:
>
> ---
>
>
>
>
>
>
>
>
>
>                                         /* Public domain code for JLKISS64
> RNG - long period KISS RNG
> producing 64-bit results */
>
>                                         unsigned long long x =
> 123456789123ULL,y = 987654321987ULL; /* Seed
> variables */
> unsigned int z1 = 43219876, c1 = 6543217, z2 = 21987643, c2 = 1732654; /*
> Seed variables */
>
>                                         unsigned long long JLKISS64()
> {
>
>                                             unsigned long long t;
>
>                                         x = 1490024343005336237ULL * x +
> 123456789;
> y ^= y << 21; y ^= y >> 17; y ^= y << 30; /* Do not set y=0! */
> t = 4294584393ULL * z1 + c1; c1 = t >> 32; z1 = t;
> t = 4246477509ULL * z2 + c2; c2 = t >> 32; z2 = t;
>
>                                         return x + y + z1 + ((unsigned
> long long)z2 << 32); /* Return 64-bit
> result */
> }
>
>
>
>
>
>
>
>
> --
> Regards,
> Robert
>
>
>
> >The implementation of rte_rand() returns only 62 bits of
> >pseudo-randomness, because the underlying calls to lrand48()
> >"return non-negative long integers uniformly distributed
> >between 0 and 2^31."
> >
> >We have written a potential fix, but before we spend more
> >time testing and refining it, I wanted to check with you
> >guys.
> >
> >We switched to using the reentrant versions of [ls]rand48,
> >and maintain per-lcore state. We need ~2.06 calls to
> >lrand48_r(), per call to rte_rand().
> >
> >Do you agree with the approach we've taken in this patch?
> >
> >
> >Thanks,
> >Robert
> >
> >---
> > lib/librte_eal/common/include/rte_random.h |   33
> >+++++++++++++++++++++++++--
> > lib/librte_eal/linuxapp/eal/eal_thread.c   |    7 ++++++
> > 2 files changed, 37 insertions(+), 3 deletions(-)
> >
> >diff --git a/lib/librte_eal/common/include/rte_random.h
> >b/lib/librte_eal/common/include/rte_random.h
> >index 24ae836..b9248cd 100644
> >--- a/lib/librte_eal/common/include/rte_random.h
> >+++ b/lib/librte_eal/common/include/rte_random.h
> >@@ -46,6 +46,17 @@ extern "C" {
> >
> > #include <stdint.h>
> > #include <stdlib.h>
> >+#include <rte_per_lcore.h>
> >+#include <rte_branch_prediction.h>
> >+
> >+struct rte_rand_data {
> >+      struct drand48_data _dr48;
> >+      uint32_t _hi_bits;
> >+      uint8_t _bits_left;
> >+};
> >+
> >+RTE_DECLARE_PER_LCORE(struct rte_rand_data, _rand_data);
> >+
> >
> > /**
> >  * Seed the pseudo-random generator.
> >@@ -60,7 +71,7 @@ extern "C" {
> > static inline void
> > rte_srand(uint64_t seedval)
> > {
> >-      srand48((long unsigned int)seedval);
> >+      srand48_r((long unsigned int)seedval,
> &RTE_PER_LCORE(_rand_data)._dr48);
> > }
> >
> > /**
> >@@ -76,10 +87,26 @@ rte_srand(uint64_t seedval)
> > static inline uint64_t
> > rte_rand(void)
> > {
> >+      struct rte_rand_data *rd = &RTE_PER_LCORE(_rand_data);
> >       uint64_t val;
> >-      val = lrand48();
> >+      uint32_t hi_bits;
> >+      long int result;
> >+
> >+      if (unlikely(rd->_bits_left < 2)) {
> >+              lrand48_r(&rd->_dr48, &result);
> >+              rd->_hi_bits |= (uint32_t)result << (1 - rd->_bits_left);
> >+              rd->_bits_left += 31;
> >+      }
> >+
> >+      hi_bits = rd->_hi_bits;
> >+      lrand48_r(&rd->_dr48, &result);
> >+      val = (uint32_t)result | (hi_bits & 0x8000000);
> >       val <<= 32;
> >-      val += lrand48();
> >+      hi_bits <<= 1;
> >+      lrand48_r(&rd->_dr48, &result);
> >+      val |= (uint32_t)result | (hi_bits & 0x8000000);
> >+      rd->_hi_bits = hi_bits << 1;
> >+      rd->_bits_left -= 2;
> >       return val;
> > }
> >
> >diff --git a/lib/librte_eal/linuxapp/eal/eal_thread.c
> >b/lib/librte_eal/linuxapp/eal/eal_thread.c
> >index 5635c7d..08e7f72 100644
> >--- a/lib/librte_eal/linuxapp/eal/eal_thread.c
> >+++ b/lib/librte_eal/linuxapp/eal/eal_thread.c
> >@@ -52,6 +52,8 @@
> > #include <rte_eal.h>
> > #include <rte_per_lcore.h>
> > #include <rte_lcore.h>
> >+#include <rte_cycles.h>
> >+#include <rte_random.h>
> >
> > #include "eal_private.h"
> > #include "eal_thread.h"
> >@@ -59,6 +61,8 @@
> > RTE_DEFINE_PER_LCORE(unsigned, _lcore_id) = LCORE_ID_ANY;
> > RTE_DEFINE_PER_LCORE(unsigned, _socket_id) = (unsigned)SOCKET_ID_ANY;
> > RTE_DEFINE_PER_LCORE(rte_cpuset_t, _cpuset);
> >+RTE_DEFINE_PER_LCORE(struct rte_rand_data, _rand_data);
> >+
> >
> > /*
> >  * Send a message to a slave lcore identified by slave_id to call a
> >@@ -147,6 +151,9 @@ eal_thread_loop(__attribute__((unused)) void *arg)
> >       /* set the lcore ID in per-lcore memory area */
> >       RTE_PER_LCORE(_lcore_id) = lcore_id;
> >
> >+      /* seed per-lcore PRNG */
> >+      rte_srand(rte_rdtsc());
> >+
> >       /* set CPU affinity */
> >       if (eal_thread_set_affinity() < 0)
> >               rte_panic("cannot set affinity\n");
> >--
> >1.7.1
> >
>
>

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
  2015-03-27 16:38 ` Sanford, Robert
  2015-03-28  0:02   ` Stephen Hemminger
@ 2015-03-28  0:03   ` Stephen Hemminger
  2015-03-28  0:38     ` Matthew Hall
  1 sibling, 1 reply; 9+ messages in thread
From: Stephen Hemminger @ 2015-03-28  0:03 UTC (permalink / raw)
  To: Sanford, Robert; +Cc: dev

I would argue remove rte_rand from DPDK.

On Fri, Mar 27, 2015 at 9:38 AM, Sanford, Robert <rsanford@akamai.com>
wrote:

> Never mind ... I cancel the previous suggestion. After further reading on
> RNGs, I believe we should abandon the use of lrand48() and implement our
> own RNG based on the so-called KISS family of RNGs originally proposed by
> the late George Marsaglia. In his excellent paper, "Good Practice in
> (Pseudo) Random Number Generation for Bioinformatics Applications", David
> Jones (UCL Bioinformatics Group) describes a few variants of KISS
> generators. This paper, and Robert G. Brown's (Duke Univ.) comprehensive
> "Dieharder" random number test suite work show that KISS RNGs are simple
> and fast, yet high quality.
>
> Something like JLKISS64(), with state kept in TLS, would be ideal for DPDK
> use. In limited experiments, I found JLKISS64() (not inlined, compiles to
> ~40 instructions) to be ~4 times faster than rte_rand(). This is probably
> because JLKISS64() achieves integer-instruction parallelism, while
> rte_rand(), with its two calls to lrand48(), nrand48_r(), and
> __drand48_iterate(), does not (and all those calls!).
>
> Here is the JLKISS64() function, as it appears in Jones's GoodPracticeRNG
> paper:
>
> ---
>
>
>
>
>
>
>
>
>
>                                         /* Public domain code for JLKISS64
> RNG - long period KISS RNG
> producing 64-bit results */
>
>                                         unsigned long long x =
> 123456789123ULL,y = 987654321987ULL; /* Seed
> variables */
> unsigned int z1 = 43219876, c1 = 6543217, z2 = 21987643, c2 = 1732654; /*
> Seed variables */
>
>                                         unsigned long long JLKISS64()
> {
>
>                                             unsigned long long t;
>
>                                         x = 1490024343005336237ULL * x +
> 123456789;
> y ^= y << 21; y ^= y >> 17; y ^= y << 30; /* Do not set y=0! */
> t = 4294584393ULL * z1 + c1; c1 = t >> 32; z1 = t;
> t = 4246477509ULL * z2 + c2; c2 = t >> 32; z2 = t;
>
>                                         return x + y + z1 + ((unsigned
> long long)z2 << 32); /* Return 64-bit
> result */
> }
>
>
>
>
>
>
>
>
> --
> Regards,
> Robert
>
>
>
> >The implementation of rte_rand() returns only 62 bits of
> >pseudo-randomness, because the underlying calls to lrand48()
> >"return non-negative long integers uniformly distributed
> >between 0 and 2^31."
> >
> >We have written a potential fix, but before we spend more
> >time testing and refining it, I wanted to check with you
> >guys.
> >
> >We switched to using the reentrant versions of [ls]rand48,
> >and maintain per-lcore state. We need ~2.06 calls to
> >lrand48_r(), per call to rte_rand().
> >
> >Do you agree with the approach we've taken in this patch?
> >
> >
> >Thanks,
> >Robert
> >
> >---
> > lib/librte_eal/common/include/rte_random.h |   33
> >+++++++++++++++++++++++++--
> > lib/librte_eal/linuxapp/eal/eal_thread.c   |    7 ++++++
> > 2 files changed, 37 insertions(+), 3 deletions(-)
> >
> >diff --git a/lib/librte_eal/common/include/rte_random.h
> >b/lib/librte_eal/common/include/rte_random.h
> >index 24ae836..b9248cd 100644
> >--- a/lib/librte_eal/common/include/rte_random.h
> >+++ b/lib/librte_eal/common/include/rte_random.h
> >@@ -46,6 +46,17 @@ extern "C" {
> >
> > #include <stdint.h>
> > #include <stdlib.h>
> >+#include <rte_per_lcore.h>
> >+#include <rte_branch_prediction.h>
> >+
> >+struct rte_rand_data {
> >+      struct drand48_data _dr48;
> >+      uint32_t _hi_bits;
> >+      uint8_t _bits_left;
> >+};
> >+
> >+RTE_DECLARE_PER_LCORE(struct rte_rand_data, _rand_data);
> >+
> >
> > /**
> >  * Seed the pseudo-random generator.
> >@@ -60,7 +71,7 @@ extern "C" {
> > static inline void
> > rte_srand(uint64_t seedval)
> > {
> >-      srand48((long unsigned int)seedval);
> >+      srand48_r((long unsigned int)seedval,
> &RTE_PER_LCORE(_rand_data)._dr48);
> > }
> >
> > /**
> >@@ -76,10 +87,26 @@ rte_srand(uint64_t seedval)
> > static inline uint64_t
> > rte_rand(void)
> > {
> >+      struct rte_rand_data *rd = &RTE_PER_LCORE(_rand_data);
> >       uint64_t val;
> >-      val = lrand48();
> >+      uint32_t hi_bits;
> >+      long int result;
> >+
> >+      if (unlikely(rd->_bits_left < 2)) {
> >+              lrand48_r(&rd->_dr48, &result);
> >+              rd->_hi_bits |= (uint32_t)result << (1 - rd->_bits_left);
> >+              rd->_bits_left += 31;
> >+      }
> >+
> >+      hi_bits = rd->_hi_bits;
> >+      lrand48_r(&rd->_dr48, &result);
> >+      val = (uint32_t)result | (hi_bits & 0x8000000);
> >       val <<= 32;
> >-      val += lrand48();
> >+      hi_bits <<= 1;
> >+      lrand48_r(&rd->_dr48, &result);
> >+      val |= (uint32_t)result | (hi_bits & 0x8000000);
> >+      rd->_hi_bits = hi_bits << 1;
> >+      rd->_bits_left -= 2;
> >       return val;
> > }
> >
> >diff --git a/lib/librte_eal/linuxapp/eal/eal_thread.c
> >b/lib/librte_eal/linuxapp/eal/eal_thread.c
> >index 5635c7d..08e7f72 100644
> >--- a/lib/librte_eal/linuxapp/eal/eal_thread.c
> >+++ b/lib/librte_eal/linuxapp/eal/eal_thread.c
> >@@ -52,6 +52,8 @@
> > #include <rte_eal.h>
> > #include <rte_per_lcore.h>
> > #include <rte_lcore.h>
> >+#include <rte_cycles.h>
> >+#include <rte_random.h>
> >
> > #include "eal_private.h"
> > #include "eal_thread.h"
> >@@ -59,6 +61,8 @@
> > RTE_DEFINE_PER_LCORE(unsigned, _lcore_id) = LCORE_ID_ANY;
> > RTE_DEFINE_PER_LCORE(unsigned, _socket_id) = (unsigned)SOCKET_ID_ANY;
> > RTE_DEFINE_PER_LCORE(rte_cpuset_t, _cpuset);
> >+RTE_DEFINE_PER_LCORE(struct rte_rand_data, _rand_data);
> >+
> >
> > /*
> >  * Send a message to a slave lcore identified by slave_id to call a
> >@@ -147,6 +151,9 @@ eal_thread_loop(__attribute__((unused)) void *arg)
> >       /* set the lcore ID in per-lcore memory area */
> >       RTE_PER_LCORE(_lcore_id) = lcore_id;
> >
> >+      /* seed per-lcore PRNG */
> >+      rte_srand(rte_rdtsc());
> >+
> >       /* set CPU affinity */
> >       if (eal_thread_set_affinity() < 0)
> >               rte_panic("cannot set affinity\n");
> >--
> >1.7.1
> >
>
>

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
  2015-03-28  0:03   ` Stephen Hemminger
@ 2015-03-28  0:38     ` Matthew Hall
  2015-03-30  5:28       ` Stephen Hemminger
  0 siblings, 1 reply; 9+ messages in thread
From: Matthew Hall @ 2015-03-28  0:38 UTC (permalink / raw)
  To: Stephen Hemminger; +Cc: dev

On Fri, Mar 27, 2015 at 05:03:02PM -0700, Stephen Hemminger wrote:
> I would argue remove rte_rand from DPDK.

+1

To paraphrase Donald Knuth, "Random numbers should not be generated [using a 
function coded] at random."

It'd be better to fix libc, or considering that has a slow dev cycle and 
platform compatibility limits, use some simple, semi-random, high-performance 
BSD licensed routine from a known-good library.

Matthew.

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
  2015-03-28  0:38     ` Matthew Hall
@ 2015-03-30  5:28       ` Stephen Hemminger
  2015-03-30 22:19         ` Robert Sanford
  0 siblings, 1 reply; 9+ messages in thread
From: Stephen Hemminger @ 2015-03-30  5:28 UTC (permalink / raw)
  To: Matthew Hall; +Cc: dev

if some one needs PRNG, th GNU scientific library has lots of them
https://www.gnu.org/software/gsl/manual/html_node/Random-number-generator-algorithms.html

On Fri, Mar 27, 2015 at 5:38 PM, Matthew Hall <mhall@mhcomputing.net> wrote:

> On Fri, Mar 27, 2015 at 05:03:02PM -0700, Stephen Hemminger wrote:
> > I would argue remove rte_rand from DPDK.
>
> +1
>
> To paraphrase Donald Knuth, "Random numbers should not be generated [using
> a
> function coded] at random."
>
> It'd be better to fix libc, or considering that has a slow dev cycle and
> platform compatibility limits, use some simple, semi-random,
> high-performance
> BSD licensed routine from a known-good library.
>
> Matthew.
>

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
  2015-03-30  5:28       ` Stephen Hemminger
@ 2015-03-30 22:19         ` Robert Sanford
  2015-03-31  1:51           ` Neil Horman
  0 siblings, 1 reply; 9+ messages in thread
From: Robert Sanford @ 2015-03-30 22:19 UTC (permalink / raw)
  To: Stephen Hemminger; +Cc: dev

Yes, applications have many choices for PRNGs. But, we still need one
internally for the following libs: PMDs (e1000, fm10k, i40e, ixgbe, virtio,
xenvirt), sched, and timer.


On Fri, Mar 27, 2015 at 8:03 PM, Stephen Hemminger <
stephen@networkplumber.org> wrote:
> I would argue remove rte_rand from DPDK.



On Mon, Mar 30, 2015 at 1:28 AM, Stephen Hemminger <
stephen@networkplumber.org> wrote:

> if some one needs PRNG, th GNU scientific library has lots of them
>
> https://www.gnu.org/software/gsl/manual/html_node/Random-number-generator-algorithms.html
>
> On Fri, Mar 27, 2015 at 5:38 PM, Matthew Hall <mhall@mhcomputing.net>
> wrote:
>
> > On Fri, Mar 27, 2015 at 05:03:02PM -0700, Stephen Hemminger wrote:
> > > I would argue remove rte_rand from DPDK.
> >
> > +1
> >
> > To paraphrase Donald Knuth, "Random numbers should not be generated
> [using
> > a
> > function coded] at random."
> >
> > It'd be better to fix libc, or considering that has a slow dev cycle and
> > platform compatibility limits, use some simple, semi-random,
> > high-performance
> > BSD licensed routine from a known-good library.
> >
> > Matthew.
> >
>

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
  2015-03-30 22:19         ` Robert Sanford
@ 2015-03-31  1:51           ` Neil Horman
  2015-04-01  2:17             ` Stephen Hemminger
  0 siblings, 1 reply; 9+ messages in thread
From: Neil Horman @ 2015-03-31  1:51 UTC (permalink / raw)
  To: Robert Sanford; +Cc: dev

On Mon, Mar 30, 2015 at 06:19:28PM -0400, Robert Sanford wrote:
> Yes, applications have many choices for PRNGs. But, we still need one
> internally for the following libs: PMDs (e1000, fm10k, i40e, ixgbe, virtio,
> xenvirt), sched, and timer.
> 
They can be updated to use the apropriate rng from an external library.
Neil

> 
> On Fri, Mar 27, 2015 at 8:03 PM, Stephen Hemminger <
> stephen@networkplumber.org> wrote:
> > I would argue remove rte_rand from DPDK.
> 
> 
> 
> On Mon, Mar 30, 2015 at 1:28 AM, Stephen Hemminger <
> stephen@networkplumber.org> wrote:
> 
> > if some one needs PRNG, th GNU scientific library has lots of them
> >
> > https://www.gnu.org/software/gsl/manual/html_node/Random-number-generator-algorithms.html
> >
> > On Fri, Mar 27, 2015 at 5:38 PM, Matthew Hall <mhall@mhcomputing.net>
> > wrote:
> >
> > > On Fri, Mar 27, 2015 at 05:03:02PM -0700, Stephen Hemminger wrote:
> > > > I would argue remove rte_rand from DPDK.
> > >
> > > +1
> > >
> > > To paraphrase Donald Knuth, "Random numbers should not be generated
> > [using
> > > a
> > > function coded] at random."
> > >
> > > It'd be better to fix libc, or considering that has a slow dev cycle and
> > > platform compatibility limits, use some simple, semi-random,
> > > high-performance
> > > BSD licensed routine from a known-good library.
> > >
> > > Matthew.
> > >
> >
> 

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits
  2015-03-31  1:51           ` Neil Horman
@ 2015-04-01  2:17             ` Stephen Hemminger
  0 siblings, 0 replies; 9+ messages in thread
From: Stephen Hemminger @ 2015-04-01  2:17 UTC (permalink / raw)
  To: Neil Horman; +Cc: dev

Plus the driver and sched uses really only need of few bits of crap random
number. Probably simple BSD random (32 bits)
is more than enough

On Mon, Mar 30, 2015 at 6:51 PM, Neil Horman <nhorman@tuxdriver.com> wrote:

> On Mon, Mar 30, 2015 at 06:19:28PM -0400, Robert Sanford wrote:
> > Yes, applications have many choices for PRNGs. But, we still need one
> > internally for the following libs: PMDs (e1000, fm10k, i40e, ixgbe,
> virtio,
> > xenvirt), sched, and timer.
> >
> They can be updated to use the apropriate rng from an external library.
> Neil
>
> >
> > On Fri, Mar 27, 2015 at 8:03 PM, Stephen Hemminger <
> > stephen@networkplumber.org> wrote:
> > > I would argue remove rte_rand from DPDK.
> >
> >
> >
> > On Mon, Mar 30, 2015 at 1:28 AM, Stephen Hemminger <
> > stephen@networkplumber.org> wrote:
> >
> > > if some one needs PRNG, th GNU scientific library has lots of them
> > >
> > >
> https://www.gnu.org/software/gsl/manual/html_node/Random-number-generator-algorithms.html
> > >
> > > On Fri, Mar 27, 2015 at 5:38 PM, Matthew Hall <mhall@mhcomputing.net>
> > > wrote:
> > >
> > > > On Fri, Mar 27, 2015 at 05:03:02PM -0700, Stephen Hemminger wrote:
> > > > > I would argue remove rte_rand from DPDK.
> > > >
> > > > +1
> > > >
> > > > To paraphrase Donald Knuth, "Random numbers should not be generated
> > > [using
> > > > a
> > > > function coded] at random."
> > > >
> > > > It'd be better to fix libc, or considering that has a slow dev cycle
> and
> > > > platform compatibility limits, use some simple, semi-random,
> > > > high-performance
> > > > BSD licensed routine from a known-good library.
> > > >
> > > > Matthew.
> > > >
> > >
> >
>

^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2015-04-01  2:17 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-03-17 16:18 [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits Robert Sanford
2015-03-27 16:38 ` Sanford, Robert
2015-03-28  0:02   ` Stephen Hemminger
2015-03-28  0:03   ` Stephen Hemminger
2015-03-28  0:38     ` Matthew Hall
2015-03-30  5:28       ` Stephen Hemminger
2015-03-30 22:19         ` Robert Sanford
2015-03-31  1:51           ` Neil Horman
2015-04-01  2:17             ` Stephen Hemminger

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