Felipe Tonello wrote: > On Mon, Oct 12, 2015 at 11:16 AM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote: >> Felipe Tonello wrote: >>> I believe that is the best way to implement. Create multiple requests >>> until the ALSA substreams buffer are empty and free the request on >>> completion. >> >> I believe a better way to implement this is to allocate a fixed number >> of requests, and to always reuse them. > > How many? Enough to get proper pipelining. At least two, maybe not more. (Depends on how fast those tiny CPUs can queue the next request.) >>> The problem of having requests when host isn't listening will happen >>> anyway because there is no way to know that until completion. >> >> But if you have no upper limit on the number of queues requests, you >> will eventually run out of (DMA) memory. > > And that's what happening at the moment. One of my patches are to fix > a memory leak when that happens. > > But it would be ideal to have a FIFO of requests and perhaps ignore > new requests if the FIFO is full. > > So, allocate (pre-allocate?) new requests until the FIFO is full. Upon > completion, remove the request from FIFO, but still reuse it on > f_midi_transmit() and queue it on the FIFO again if there is still > data from ALSA, otherwise just free the request. Yes, that's exactly what I'm proposing. Regards, Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
