[ltt-dev] [URCU RFC patch 1/3] call_rcu: use cpu affinity for per-cpu call_rcu threads
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Mon Jun 6 16:47:48 EDT 2011
* Paul E. McKenney (paulmck at linux.vnet.ibm.com) wrote:
> On Mon, Jun 06, 2011 at 01:45:59PM -0400, Mathieu Desnoyers wrote:
> > I played a bit with the call_rcu() implementation alongside with my
> > rbtree tests, and noticed the following:
> >
> > If I use per-cpu call_rcu threads with URCU_CALL_RCU_RT flag, with one
> > updater thread only for my rbtree (no reader), I get 38365 updates/s.
> > If I add cpu affinity to these per-cpu call_rcu threads (I have prepared
> > a patch that does this), it jumps to 54219 updates/s. So it looks like
> > keeping per-cpu affinity for the call_rcu thread is a good thing.
>
> Makes sense to me!
>
> Main comment is that API.h should also be updated.
I updated API.txt. What is API.h ?
Mathieu
>
> Thanx, Paul
>
> > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
> > ---
> > API.txt | 7 +++++--
> > tests/rcutorture.h | 4 ++--
> > urcu-call-rcu-impl.h | 51 ++++++++++++++++++++++++++++++++++++++++++++-------
> > urcu-call-rcu.h | 3 ++-
> > urcu-qsbr.c | 1 +
> > urcu.c | 1 +
> > 6 files changed, 55 insertions(+), 12 deletions(-)
> >
> > Index: userspace-rcu/API.txt
> > ===================================================================
> > --- userspace-rcu.orig/API.txt
> > +++ userspace-rcu/API.txt
> > @@ -59,12 +59,15 @@ void call_rcu(struct rcu_head *head,
> >
> > call_rcu(&p->rcu, func);
> >
> > -struct call_rcu_data *create_call_rcu_data(unsigned long flags);
> > +struct call_rcu_data *create_call_rcu_data(unsigned long flags,
> > + int cpu_affinity);
> >
> > Returns a handle that can be passed to the following
> > primitives. The "flags" argument can be zero, or can be
> > URCU_CALL_RCU_RT if the worker threads associated with the
> > - new helper thread are to get real-time response.
> > + new helper thread are to get real-time response. The argument
> > + "cpu_affinity" specifies a cpu on which the call_rcu thread should
> > + be affined to. It is ignored if negative.
> >
> > struct call_rcu_data *get_default_call_rcu_data(void);
> >
> > Index: userspace-rcu/tests/rcutorture.h
> > ===================================================================
> > --- userspace-rcu.orig/tests/rcutorture.h
> > +++ userspace-rcu/tests/rcutorture.h
> > @@ -156,7 +156,7 @@ void *rcu_update_perf_test(void *arg)
> > if ((random() & 0xf00) == 0) {
> > struct call_rcu_data *crdp;
> >
> > - crdp = create_call_rcu_data(0);
> > + crdp = create_call_rcu_data(0, -1);
> > if (crdp != NULL) {
> > fprintf(stderr,
> > "Using per-thread call_rcu() worker.\n");
> > @@ -385,7 +385,7 @@ void *rcu_fake_update_stress_test(void *
> > if ((random() & 0xf00) == 0) {
> > struct call_rcu_data *crdp;
> >
> > - crdp = create_call_rcu_data(0);
> > + crdp = create_call_rcu_data(0, -1);
> > if (crdp != NULL) {
> > fprintf(stderr,
> > "Using per-thread call_rcu() worker.\n");
> > Index: userspace-rcu/urcu-call-rcu-impl.h
> > ===================================================================
> > --- userspace-rcu.orig/urcu-call-rcu-impl.h
> > +++ userspace-rcu/urcu-call-rcu-impl.h
> > @@ -20,6 +20,7 @@
> > * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> > */
> >
> > +#define _GNU_SOURCE
> > #include <stdio.h>
> > #include <pthread.h>
> > #include <signal.h>
> > @@ -31,6 +32,7 @@
> > #include <sys/time.h>
> > #include <syscall.h>
> > #include <unistd.h>
> > +#include <sched.h>
> >
> > #include "config.h"
> > #include "urcu/wfqueue.h"
> > @@ -47,6 +49,7 @@ struct call_rcu_data {
> > pthread_cond_t cond;
> > unsigned long qlen;
> > pthread_t tid;
> > + int cpu_affinity;
> > struct cds_list_head list;
> > } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
> >
> > @@ -146,6 +149,31 @@ static void call_rcu_unlock(pthread_mute
> > }
> > }
> >
> > +#if HAVE_SCHED_SETAFFINITY
> > +static
> > +int set_thread_cpu_affinity(struct call_rcu_data *crdp)
> > +{
> > + cpu_set_t mask;
> > +
> > + if (crdp->cpu_affinity < 0)
> > + return 0;
> > +
> > + CPU_ZERO(&mask);
> > + CPU_SET(crdp->cpu_affinity, &mask);
> > +#if SCHED_SETAFFINITY_ARGS == 2
> > + return sched_setaffinity(0, &mask);
> > +#else
> > + return sched_setaffinity(0, sizeof(mask), &mask);
> > +#endif
> > +}
> > +#else
> > +static
> > +int set_thread_cpu_affinity(struct call_rcu_data *crdp)
> > +{
> > + return 0;
> > +}
> > +#endif
> > +
> > /* This is the code run by each call_rcu thread. */
> >
> > static void *call_rcu_thread(void *arg)
> > @@ -156,6 +184,11 @@ static void *call_rcu_thread(void *arg)
> > struct call_rcu_data *crdp = (struct call_rcu_data *)arg;
> > struct rcu_head *rhp;
> >
> > + if (set_thread_cpu_affinity(crdp) != 0) {
> > + perror("pthread_setaffinity_np");
> > + exit(-1);
> > + }
> > +
> > thread_call_rcu_data = crdp;
> > for (;;) {
> > if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
> > @@ -214,7 +247,8 @@ static void *call_rcu_thread(void *arg)
> > */
> >
> > static void call_rcu_data_init(struct call_rcu_data **crdpp,
> > - unsigned long flags)
> > + unsigned long flags,
> > + int cpu_affinity)
> > {
> > struct call_rcu_data *crdp;
> >
> > @@ -236,6 +270,7 @@ static void call_rcu_data_init(struct ca
> > }
> > crdp->flags = flags | URCU_CALL_RCU_RUNNING;
> > cds_list_add(&crdp->list, &call_rcu_data_list);
> > + crdp->cpu_affinity = cpu_affinity;
> > cmm_smp_mb(); /* Structure initialized before pointer is planted. */
> > *crdpp = crdp;
> > if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) {
> > @@ -280,20 +315,22 @@ pthread_t get_call_rcu_thread(struct cal
> > * Create a call_rcu_data structure (with thread) and return a pointer.
> > */
> >
> > -static struct call_rcu_data *__create_call_rcu_data(unsigned long flags)
> > +static struct call_rcu_data *__create_call_rcu_data(unsigned long flags,
> > + int cpu_affinity)
> > {
> > struct call_rcu_data *crdp;
> >
> > - call_rcu_data_init(&crdp, flags);
> > + call_rcu_data_init(&crdp, flags, cpu_affinity);
> > return crdp;
> > }
> >
> > -struct call_rcu_data *create_call_rcu_data(unsigned long flags)
> > +struct call_rcu_data *create_call_rcu_data(unsigned long flags,
> > + int cpu_affinity)
> > {
> > struct call_rcu_data *crdp;
> >
> > call_rcu_lock(&call_rcu_mutex);
> > - crdp = __create_call_rcu_data(flags);
> > + crdp = __create_call_rcu_data(flags, cpu_affinity);
> > call_rcu_unlock(&call_rcu_mutex);
> > return crdp;
> > }
> > @@ -346,7 +383,7 @@ struct call_rcu_data *get_default_call_r
> > call_rcu_unlock(&call_rcu_mutex);
> > return default_call_rcu_data;
> > }
> > - call_rcu_data_init(&default_call_rcu_data, 0);
> > + call_rcu_data_init(&default_call_rcu_data, 0, -1);
> > call_rcu_unlock(&call_rcu_mutex);
> > return default_call_rcu_data;
> > }
> > @@ -434,7 +471,7 @@ int create_all_cpu_call_rcu_data(unsigne
> > call_rcu_unlock(&call_rcu_mutex);
> > continue;
> > }
> > - crdp = __create_call_rcu_data(flags);
> > + crdp = __create_call_rcu_data(flags, i);
> > if (crdp == NULL) {
> > call_rcu_unlock(&call_rcu_mutex);
> > errno = ENOMEM;
> > Index: userspace-rcu/urcu-call-rcu.h
> > ===================================================================
> > --- userspace-rcu.orig/urcu-call-rcu.h
> > +++ userspace-rcu/urcu-call-rcu.h
> > @@ -64,7 +64,8 @@ struct rcu_head {
> > */
> > struct call_rcu_data *get_cpu_call_rcu_data(int cpu);
> > pthread_t get_call_rcu_thread(struct call_rcu_data *crdp);
> > -struct call_rcu_data *create_call_rcu_data(unsigned long flags);
> > +struct call_rcu_data *create_call_rcu_data(unsigned long flags,
> > + int cpu_affinity);
> > int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp);
> > struct call_rcu_data *get_default_call_rcu_data(void);
> > struct call_rcu_data *get_call_rcu_data(void);
> > Index: userspace-rcu/urcu-qsbr.c
> > ===================================================================
> > --- userspace-rcu.orig/urcu-qsbr.c
> > +++ userspace-rcu/urcu-qsbr.c
> > @@ -23,6 +23,7 @@
> > * IBM's contributions to this file may be relicensed under LGPLv2 or later.
> > */
> >
> > +#define _GNU_SOURCE
> > #include <stdio.h>
> > #include <pthread.h>
> > #include <signal.h>
> > Index: userspace-rcu/urcu.c
> > ===================================================================
> > --- userspace-rcu.orig/urcu.c
> > +++ userspace-rcu/urcu.c
> > @@ -24,6 +24,7 @@
> > */
> >
> > #define _BSD_SOURCE
> > +#define _GNU_SOURCE
> > #include <stdio.h>
> > #include <pthread.h>
> > #include <signal.h>
> >
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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