From: Joe Stringer Date: Fri, 15 Nov 2013 23:25:00 +0000 (-0800) Subject: coverage: Synchronize per-thread counters less aggressively X-Git-Tag: sliver-openvswitch-2.0.90-1~4^2~8 X-Git-Url: http://git.onelab.eu/?p=sliver-openvswitch.git;a=commitdiff_plain;h=bc0d88eece4d6f0a5703d59102a7cf8f1f8c7372 coverage: Synchronize per-thread counters less aggressively When profiling CPU usage in situations involving high numbers of ports, coverage_clear() was highlighted as a commonly called function. It appears that it can be quite expensive to access all of the per-thread coverage counters when threads are constantly waking up. This patch makes each thread only do coverage_clear() logic roughly once per second by introducing per-thread timers. Upcall handler counters may become less accurate, as these threads may sleep without synchronising and not wake up for some time. When the main thread is under load at ~90% CPU, this drops to ~85%. Upcall handler threads sitting at ~2.5% drop to ~1.5%. Signed-off-by: Joe Stringer Signed-off-by: Ben Pfaff --- diff --git a/lib/coverage.c b/lib/coverage.c index 43647344b..80316ef78 100644 --- a/lib/coverage.c +++ b/lib/coverage.c @@ -63,6 +63,7 @@ struct coverage_counter *coverage_counters[] = { static struct ovs_mutex coverage_mutex = OVS_MUTEX_INITIALIZER; +DEFINE_STATIC_PER_THREAD_DATA(long long int, coverage_clear_time, LLONG_MIN); static long long int coverage_run_time = LLONG_MIN; /* Index counter used to compute the moving average array's index. */ @@ -258,17 +259,33 @@ coverage_read(struct svec *lines) free(totals); } +/* Runs approximately every COVERAGE_CLEAR_INTERVAL amount of time to + * synchronize per-thread counters with global counters. Every thread maintains + * a separate timer to ensure all counters are periodically aggregated. */ void coverage_clear(void) { - size_t i; + long long int now, *thread_time; - ovs_mutex_lock(&coverage_mutex); - for (i = 0; i < n_coverage_counters; i++) { - struct coverage_counter *c = coverage_counters[i]; - c->total += c->count(); + now = time_msec(); + thread_time = coverage_clear_time_get(); + + /* Initialize the coverage_clear_time. */ + if (*thread_time == LLONG_MIN) { + *thread_time = now + COVERAGE_CLEAR_INTERVAL; + } + + if (now >= *thread_time) { + size_t i; + + ovs_mutex_lock(&coverage_mutex); + for (i = 0; i < n_coverage_counters; i++) { + struct coverage_counter *c = coverage_counters[i]; + c->total += c->count(); + } + ovs_mutex_unlock(&coverage_mutex); + *thread_time = now + COVERAGE_CLEAR_INTERVAL; } - ovs_mutex_unlock(&coverage_mutex); } /* Runs approximately every COVERAGE_RUN_INTERVAL amount of time to update the diff --git a/lib/coverage.h b/lib/coverage.h index 163728eba..4e6c05064 100644 --- a/lib/coverage.h +++ b/lib/coverage.h @@ -36,6 +36,9 @@ #define COVERAGE_RUN_INTERVAL 5000 BUILD_ASSERT_DECL(60000 % COVERAGE_RUN_INTERVAL == 0); +#define COVERAGE_CLEAR_INTERVAL 1000 +BUILD_ASSERT_DECL(COVERAGE_RUN_INTERVAL % COVERAGE_CLEAR_INTERVAL == 0); + /* Defines the moving average array length. */ #define MIN_AVG_LEN (60000/COVERAGE_RUN_INTERVAL) #define HR_AVG_LEN 60 diff --git a/tests/ofproto-dpif.at b/tests/ofproto-dpif.at index 9a7c8ffdf..b78e15653 100644 --- a/tests/ofproto-dpif.at +++ b/tests/ofproto-dpif.at @@ -926,12 +926,6 @@ arp,metadata=0,in_port=0,vlan_tci=0x0000,dl_src=80:88:88:88:88:88,dl_dst=ff:ff:f arp,metadata=0,in_port=0,vlan_tci=0x0000,dl_src=80:88:88:88:88:88,dl_dst=ff:ff:ff:ff:ff:ff,arp_spa=192.168.128.1,arp_tpa=192.168.0.2,arp_op=2,arp_sha=50:54:00:00:00:05,arp_tha=40:44:44:44:44:41 ]) -# Check that each of the packets actually passed through the slow-path. -AT_CHECK([ovs-appctl coverage/show], [0], [stdout]) -AT_CHECK([sed -n 's/[[ ]]\{2,\}/ /g -s/^dpif_execute_with_help.*total: //p' stdout], [0], [3 -]) - OVS_VSWITCHD_STOP AT_CLEANUP