On Tue, Nov 20, 2012 at 5:55 PM, Ralph Castain <r...@open-mpi.org> wrote: > Hi folks > > We have a case where we are running two parallel threads, each looping on > their own event base (we have the libevent thread support enabled). Even > though the two bases are running in separate threads, however, we see an > impact on response time - i.e., if we run only one thread, events in that > event base are serviced faster than when the other thread is in operation, > even if no events in that thread are active. > > Just to be clear, the two cases are: > > Case 1 > A single event base is created, and a single event loop is running. Two file > descriptors are being monitored by separate events - when one file descriptor > has data, that event is "activated" to handle the data. Data is only arriving > at one file descriptor, so the other one is "quiet". > > Case 2 > Two event bases are created, each being looped by an independent thread. Each > base is monitoring a different file descriptor. Only one file descriptor (for > the same base as above) is receiving data - the other base/thread is blocked > in select. We see a measurable increase in the time it takes for the "active" > event to be serviced when compared to Case 1 - the difference is roughly 20%. > > Is this cross-interaction expected? Any suggestions on how we might better > separate the two channels?
Mysterious! It's sure not expected that there would be that much of a drop-off. I'd try to look harder to diagnose what's going on. Stuff to look at would include: * What OS is this? You mentioned "select" which makes me think Windows, but you didn't actually say. * Can you trace system calls in the thread that is supposed to be idle? Have you verified that it's really sleeping on select, or is that an inference? (It's a reasonable inference, mind you, but when debugging, we shouldn't trust any inferences without checking.) * Can you profile the code, and find out which piece exactly is taking longer here? -- Nick *********************************************************************** To unsubscribe, send an e-mail to majord...@freehaven.net with unsubscribe libevent-users in the body.
