| Message ID | 1426609081-47774-1-git-send-email-rsanford@akamai.com (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers |
Return-Path: <dev-bounces@dpdk.org> X-Original-To: patchwork@dpdk.org Delivered-To: patchwork@dpdk.org Received: from [92.243.14.124] (localhost [IPv6:::1]) by dpdk.org (Postfix) with ESMTP id 61DC49AA8; Tue, 17 Mar 2015 17:18:10 +0100 (CET) Received: from mail-ig0-f172.google.com (mail-ig0-f172.google.com [209.85.213.172]) by dpdk.org (Postfix) with ESMTP id 106D89AA1 for <dev@dpdk.org>; Tue, 17 Mar 2015 17:18:09 +0100 (CET) Received: by igbue6 with SMTP id ue6so16908177igb.1 for <dev@dpdk.org>; Tue, 17 Mar 2015 09:18:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:subject:date:message-id; bh=CCtbm/jjPQnAgL6mkI9qyovSfKBmYWxLHtDzKT4drtA=; b=MLswc1flHB6qoZXDSBgyhp/pUVYmqz87Fad1aL56KWsxKNOIklLvDXYfLn/2FHgFiU raaXzG94jrENfUV5+cKdOW4xFG6ml6kM27ShkU+Drs1Q6eKBpsRqhAZ45SZmYUYpaHLP RmFPnmREHnLiFsS97x1qtgqvTLr4Gy3sFxpKPz6FM07ixy2ZmIhCVwyKZp5aKRFDMOgC LoQyUCtqr0MgG6U+5O7ocfOdhQ6a4jwev0u+4GbAQJqOykTc7FMJ3czm8Ryll7wyGS5p 9nUyCi2OyYqHLWSHjmxP8j13tAOx/AIH9K9OKxQSUeQ7t2QIaeFjqr17i18mpzUGc0PZ K8XA== X-Received: by 10.50.30.130 with SMTP id s2mr121450263igh.11.1426609088384; Tue, 17 Mar 2015 09:18:08 -0700 (PDT) Received: from localhost.localdomain ([23.79.237.14]) by mx.google.com with ESMTPSA id x10sm1359998igl.13.2015.03.17.09.18.06 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 17 Mar 2015 09:18:07 -0700 (PDT) From: Robert Sanford <rsanford2@gmail.com> X-Google-Original-From: Robert Sanford <rsanford@akamai.com> To: David.Marchand@6wind.com, Bruce.Richardson@intel.com, dev@dpdk.org Date: Tue, 17 Mar 2015 12:18:01 -0400 Message-Id: <1426609081-47774-1-git-send-email-rsanford@akamai.com> X-Mailer: git-send-email 1.7.1 Subject: [dpdk-dev] [RFC PATCH] eal: rte_rand yields only 62 random bits X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK <dev.dpdk.org> List-Unsubscribe: <http://dpdk.org/ml/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://dpdk.org/ml/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <http://dpdk.org/ml/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org Sender: "dev" <dev-bounces@dpdk.org> |
Commit Message
Robert Sanford
March 17, 2015, 4:18 p.m. UTC
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(-)
Comments
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
>
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 > > > >
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 > > > >
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.
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. >
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. > > >
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. > > > > > >
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. > > > > > > > > > >
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");