On Sun, 17 Mar 2013, Soeren Moch wrote: > For each device only one isochronous endpoint is used (EP IN4, 1x 940 > Bytes, Interval 1). > When the ENOMEM error occurs, a huge number of iTDs is in the free_list > of one stream. This number is much higher than the 2*M entries, which > should be there according to your description. Okay, but how did they get there? With each URB requiring 9 iTDs, and about 5 URBs active at any time, there should be about 5*9 = 45 iTDs in use and 2*9 = 18 iTDs on the free list. By the time each URB completes, it should have released all 9 iTDs back to the free list, and each time an URB is submitted, it should be able to acquire all 9 of the iTDs that it needs from the free list -- it shouldn't have to allocate any from the DMA pool. Looks like you'll have to investigate what's going on inside itd_urb_transaction(). Print out some useful information whenever the size of stream->free_list is above 50, such as the value of num_itds, how many of the loop iterations could get an iTD from the free list, and the value of itd->frame in the case where the "goto alloc_itd" statement is followed. It might be a good idea also to print out the size of the free list in itd_complete(), where it calls ehci_urb_done(), and include the value of ehci->now_frame. Alan Stern -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>