| Message ID | 20220601164429.759054-1-msantana@redhat.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [ovs-dev,1/2] handlers: Create additional handler threads when using CPU isolation | expand |
| Context | Check | Description |
|---|---|---|
| ovsrobot/apply-robot | success | apply and check: success |
| ovsrobot/github-robot-_Build_and_Test | success | github build: passed |
| ovsrobot/intel-ovs-compilation | success | test: success |
Michael Santana <msantana@redhat.com> writes: > Additional threads are required to service upcalls when we have CPU > isolation (in per-cpu dispatch mode). The formula used to calculate > the number of handler threads to create is as follows > > handlers_n = min(next_prime(active_cores+1), total_cores) > > Where next_prime is a function that returns the next numeric prime > number that is strictly greater than active_cores > > Assume default behavior when total_cores <= 2, that is do not create > additional threads when we have less than 2 total cores on the system > > Fixes: b1e517bd2f81 ("dpif-netlink: Introduce per-cpu upcall dispatch.") > Signed-off-by: Michael Santana <msantana@redhat.com> > --- > lib/dpif-netlink.c | 87 ++++++++++++++++++++++++++++++++++++++++++++-- > lib/ovs-thread.c | 16 +++++++++ > lib/ovs-thread.h | 1 + > 3 files changed, 102 insertions(+), 2 deletions(-) > > diff --git a/lib/dpif-netlink.c b/lib/dpif-netlink.c > index 06e1e8ca0..355ad1d09 100644 > --- a/lib/dpif-netlink.c > +++ b/lib/dpif-netlink.c > @@ -31,6 +31,7 @@ > #include <sys/epoll.h> > #include <sys/stat.h> > #include <unistd.h> > +#include <math.h> > > #include "bitmap.h" > #include "dpif-netlink-rtnl.h" > @@ -2506,6 +2507,88 @@ dpif_netlink_handler_uninit(struct dpif_handler *handler) > } > #endif > > +/* > + * Returns 1 if num is a prime number, > + * Otherwise return 0 > + */ > +static uint32_t > +is_prime(uint32_t num) > +{ > + if ((num < 2) || ((num % 2) == 0)) { > + return num == 2; > + } > + > + uint32_t i; > + uint32_t limit = sqrt((float) num); > + for (i = 3; i <= limit; i += 2) { > + if (num % i == 0) { > + return 0; > + } > + } > + > + return 1; > +} > + > +/* > + * Returns num if num is a prime number. Otherwise returns the next > + * prime greater than num. Search is limited by the limit variable. > + * > + * Returns 0 if num >= limit, or if no prime has been found between > + * num and limit > + */ > +static uint32_t > +next_prime(uint32_t num, uint32_t limit) > +{ > + if (num < 2) { > + return 2; > + } > + if (num == 2) { > + return 3; > + } > + if (num % 2 == 0) { > + num++; > + } > + > + uint32_t i; > + for (i = num; i < limit; i += 2) { > + if (is_prime(i)) { > + return i; > + } > + } > + > + return 0; > +} > + > +/* > + * Calcuales and returns the number of handler threads needed based > + * the following formula: > + * > + * handlers_n = min(next_prime(active_cores+1), total_cores) > + * > + * Where next_prime is a function that returns the next numeric prime > + * number that is strictly greater than active_cores > + */ > +static uint32_t > +dpif_netlink_calculate_handlers_num(void) > +{ > + uint32_t next_prime_num; > + uint32_t n_handlers = count_cpu_cores(); > + uint32_t total_cores = count_total_cores(); > + > + /* > + * If we have isolated cores, add additional handler threads to > + * service inactive cores in the unlikely event that traffic goes > + * through inactive cores > + */ > + if (n_handlers < total_cores && total_cores > 2) { > + next_prime_num = next_prime(n_handlers +1, 10000000); Please insert a space after the '+' Also, there should be some kind of comment why '10000000' was chosen (perhaps a #define or const instead of a raw number as well). With those addressed, Acked-by: Aaron Conole <aconole@redhat.com> > + n_handlers = next_prime_num >= total_cores ? > + total_cores : next_prime_num; > + } > + > + return n_handlers; > +} > + > static int > dpif_netlink_refresh_handlers_cpu_dispatch(struct dpif_netlink *dpif) > OVS_REQ_WRLOCK(dpif->upcall_lock) > @@ -2515,7 +2598,7 @@ dpif_netlink_refresh_handlers_cpu_dispatch(struct dpif_netlink *dpif) > uint32_t n_handlers; > uint32_t *upcall_pids; > > - n_handlers = count_cpu_cores(); > + n_handlers = dpif_netlink_calculate_handlers_num(); > if (dpif->n_handlers != n_handlers) { > VLOG_DBG("Dispatch mode(per-cpu): initializing %d handlers", > n_handlers); > @@ -2755,7 +2838,7 @@ dpif_netlink_number_handlers_required(struct dpif *dpif_, uint32_t *n_handlers) > struct dpif_netlink *dpif = dpif_netlink_cast(dpif_); > > if (dpif_netlink_upcall_per_cpu(dpif)) { > - *n_handlers = count_cpu_cores(); > + *n_handlers = dpif_netlink_calculate_handlers_num(); > return true; > } > > diff --git a/lib/ovs-thread.c b/lib/ovs-thread.c > index 805cba622..2172b3d3f 100644 > --- a/lib/ovs-thread.c > +++ b/lib/ovs-thread.c > @@ -663,6 +663,22 @@ count_cpu_cores(void) > return n_cores > 0 ? n_cores : 0; > } > > +/* Returns the total number of cores on the system, or 0 if the > + * number cannot be determined. */ > +int > +count_total_cores(void) { > + long int n_cores; > + > +#ifndef _WIN32 > + n_cores = sysconf(_SC_NPROCESSORS_CONF); > +#else > + n_cores = 0; > + errno = ENOTSUP; > +#endif > + > + return n_cores > 0 ? n_cores : 0; > +} > + > /* Returns 'true' if current thread is PMD thread. */ > bool > thread_is_pmd(void) > diff --git a/lib/ovs-thread.h b/lib/ovs-thread.h > index 3b444ccdc..aac5e19c9 100644 > --- a/lib/ovs-thread.h > +++ b/lib/ovs-thread.h > @@ -522,6 +522,7 @@ bool may_fork(void); > /* Useful functions related to threading. */ > > int count_cpu_cores(void); > +int count_total_cores(void); > bool thread_is_pmd(void); > > #endif /* ovs-thread.h */
diff --git a/lib/dpif-netlink.c b/lib/dpif-netlink.c index 06e1e8ca0..355ad1d09 100644 --- a/lib/dpif-netlink.c +++ b/lib/dpif-netlink.c @@ -31,6 +31,7 @@ #include <sys/epoll.h> #include <sys/stat.h> #include <unistd.h> +#include <math.h> #include "bitmap.h" #include "dpif-netlink-rtnl.h" @@ -2506,6 +2507,88 @@ dpif_netlink_handler_uninit(struct dpif_handler *handler) } #endif +/* + * Returns 1 if num is a prime number, + * Otherwise return 0 + */ +static uint32_t +is_prime(uint32_t num) +{ + if ((num < 2) || ((num % 2) == 0)) { + return num == 2; + } + + uint32_t i; + uint32_t limit = sqrt((float) num); + for (i = 3; i <= limit; i += 2) { + if (num % i == 0) { + return 0; + } + } + + return 1; +} + +/* + * Returns num if num is a prime number. Otherwise returns the next + * prime greater than num. Search is limited by the limit variable. + * + * Returns 0 if num >= limit, or if no prime has been found between + * num and limit + */ +static uint32_t +next_prime(uint32_t num, uint32_t limit) +{ + if (num < 2) { + return 2; + } + if (num == 2) { + return 3; + } + if (num % 2 == 0) { + num++; + } + + uint32_t i; + for (i = num; i < limit; i += 2) { + if (is_prime(i)) { + return i; + } + } + + return 0; +} + +/* + * Calcuales and returns the number of handler threads needed based + * the following formula: + * + * handlers_n = min(next_prime(active_cores+1), total_cores) + * + * Where next_prime is a function that returns the next numeric prime + * number that is strictly greater than active_cores + */ +static uint32_t +dpif_netlink_calculate_handlers_num(void) +{ + uint32_t next_prime_num; + uint32_t n_handlers = count_cpu_cores(); + uint32_t total_cores = count_total_cores(); + + /* + * If we have isolated cores, add additional handler threads to + * service inactive cores in the unlikely event that traffic goes + * through inactive cores + */ + if (n_handlers < total_cores && total_cores > 2) { + next_prime_num = next_prime(n_handlers +1, 10000000); + n_handlers = next_prime_num >= total_cores ? + total_cores : next_prime_num; + } + + return n_handlers; +} + static int dpif_netlink_refresh_handlers_cpu_dispatch(struct dpif_netlink *dpif) OVS_REQ_WRLOCK(dpif->upcall_lock) @@ -2515,7 +2598,7 @@ dpif_netlink_refresh_handlers_cpu_dispatch(struct dpif_netlink *dpif) uint32_t n_handlers; uint32_t *upcall_pids; - n_handlers = count_cpu_cores(); + n_handlers = dpif_netlink_calculate_handlers_num(); if (dpif->n_handlers != n_handlers) { VLOG_DBG("Dispatch mode(per-cpu): initializing %d handlers", n_handlers); @@ -2755,7 +2838,7 @@ dpif_netlink_number_handlers_required(struct dpif *dpif_, uint32_t *n_handlers) struct dpif_netlink *dpif = dpif_netlink_cast(dpif_); if (dpif_netlink_upcall_per_cpu(dpif)) { - *n_handlers = count_cpu_cores(); + *n_handlers = dpif_netlink_calculate_handlers_num(); return true; } diff --git a/lib/ovs-thread.c b/lib/ovs-thread.c index 805cba622..2172b3d3f 100644 --- a/lib/ovs-thread.c +++ b/lib/ovs-thread.c @@ -663,6 +663,22 @@ count_cpu_cores(void) return n_cores > 0 ? n_cores : 0; } +/* Returns the total number of cores on the system, or 0 if the + * number cannot be determined. */ +int +count_total_cores(void) { + long int n_cores; + +#ifndef _WIN32 + n_cores = sysconf(_SC_NPROCESSORS_CONF); +#else + n_cores = 0; + errno = ENOTSUP; +#endif + + return n_cores > 0 ? n_cores : 0; +} + /* Returns 'true' if current thread is PMD thread. */ bool thread_is_pmd(void) diff --git a/lib/ovs-thread.h b/lib/ovs-thread.h index 3b444ccdc..aac5e19c9 100644 --- a/lib/ovs-thread.h +++ b/lib/ovs-thread.h @@ -522,6 +522,7 @@ bool may_fork(void); /* Useful functions related to threading. */ int count_cpu_cores(void); +int count_total_cores(void); bool thread_is_pmd(void); #endif /* ovs-thread.h */
Additional threads are required to service upcalls when we have CPU isolation (in per-cpu dispatch mode). The formula used to calculate the number of handler threads to create is as follows handlers_n = min(next_prime(active_cores+1), total_cores) Where next_prime is a function that returns the next numeric prime number that is strictly greater than active_cores Assume default behavior when total_cores <= 2, that is do not create additional threads when we have less than 2 total cores on the system Fixes: b1e517bd2f81 ("dpif-netlink: Introduce per-cpu upcall dispatch.") Signed-off-by: Michael Santana <msantana@redhat.com> --- lib/dpif-netlink.c | 87 ++++++++++++++++++++++++++++++++++++++++++++-- lib/ovs-thread.c | 16 +++++++++ lib/ovs-thread.h | 1 + 3 files changed, 102 insertions(+), 2 deletions(-)