On Wed, Sep 24, 2014 at 10:39:13AM -0400, Tejun Heo wrote: > Hello, Alexander. > > On Wed, Sep 24, 2014 at 03:08:44PM +0100, Alexander Gordeev wrote: > > > Hmmm, how would the whole system benefit from it if there's only > > > single device? Each individual servicing of the interrupt does more > > > now which includes scheduling which may end up adding to completion > > > latency. > > > > As Chuck noticed, non-AHCI hardware context handlers will benefit. > > Maybe I'm off but I'm kinda skeptical that we'd be gaining back the > overhead we pay by punting to a thread. Hi Tejun, As odd as it sounds, I did not mention there is *no* change in IO performance at all (in my system): neither with one drive nor two. The change is only about how the interrupt handlers co-exist with other devices. I am attaching excerpts from some new perf tests I have done (this time in legacy interrupt mode). As you can notice, ahci_interrupt() CPU time drops from 4% to none. As of your concern wrt threaded handler invocation overhead - I am not quite sure here, but if SCHED_FIFO policy (the handler runs with) makes the difference? Anyway, as said above the overall IO does not suffer. > -- > tejun -- Regards, Alexander Gordeev agordeev@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
