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Update default broker threading configuration

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Now defaults to a max of 4 threads typically indepedent of core
count (previously could go up to a hard cap of 8).  Also now allow
controlling this setting via BRO_BROKER_MAX_THREADS environment
variable.
This commit is contained in:
Jon Siwek 2018-08-10 17:08:26 -05:00
parent 9f12b56105
commit 083947af41
2 changed files with 26 additions and 17 deletions
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8
scripts/base/frameworks/broker/main.bro
View file

@ -56,9 +56,11 @@ export {
## control mechanisms).
const congestion_queue_size = 200 &redef;
## Max number of threads to use for Broker/CAF functionality.
## Using zero will cause this to be automatically determined
## based on number of available CPUs.
## Max number of threads to use for Broker/CAF functionality. Setting to
## zero implies using the value of BRO_BROKER_MAX_THREADS environment
## variable, if set, or else typically defaults to 4 (actually 2 threads
## when simply reading offline pcaps as there's not expected to be any
## communication and more threads just adds more overhead).
const max_threads = 0 &redef;
## Max number of microseconds for under-utilized Broker/CAF

27
src/broker/Manager.cc
View file

@ -184,22 +184,29 @@ void Manager::InitPostScript()
config.set("scheduler.max-threads", max_threads);
else
{
// On high-core-count systems, spawning one thread per core
auto max_threads_env = getenv("BRO_BROKER_MAX_THREADS");
if ( max_threads_env )
config.set("scheduler.max-threads", atoi(max_threads_env));
else
{
// On high-core-count systems, letting CAF spawn a thread per core
// can lead to significant performance problems even if most
// threads are under-utilized. Related:
// https://github.com/actor-framework/actor-framework/issues/699
if ( reading_pcaps )
config.set("scheduler.max-threads", 2u);
else
{
auto hc = std::thread::hardware_concurrency();
if ( hc > 8u )
hc = 8u;
else if ( hc < 4u)
hc = 4u;
config.set("scheduler.max-threads", hc);
// If the goal was to map threads to actors, 4 threads seems
// like a minimal default that could make sense -- the main
// actors that should be doing work are (1) the core,
// (2) the subscriber, (3) data stores (actually made of
// a frontend + proxy actor). Number of data stores may
// actually vary, but lumped togather for simplicity. A (4)
// may be CAF's multiplexing or other internals...
// 4 is also the minimum number that CAF uses by default,
// even for systems with less than 4 cores.
config.set("scheduler.max-threads", 4u);
}
}