> > > > 1. call select() on completion channel with zero > timeout and return 0. > > 2. call ibv_poll_cq() directly and return 0. > > > > Question: > > > > Which way has lower overhead ? > ibv_poll_cq > > We know select() has to switch to kernel mode, does ibv_poll_cq() > > switch to kernel mode and may cause a context switch ? > > > No - it's pure user space function
But I just check the source code, ibv_poll_cq() is actually ibv_cmd_poll_cq(), and ibv_cmd_poll_cq() calls write() system call on the IB device. Doesn't this write() system call switch to kernel mode and possiblely casuse a context switch ? --CQ > > Tziporet _______________________________________________ general mailing list [email protected] http://lists.openfabrics.org/cgi-bin/mailman/listinfo/general To unsubscribe, please visit http://openib.org/mailman/listinfo/openib-general
