On Sun, 17 Mar 2013, Alan Stern wrote: > 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. One thing I forgot to mention: It would help to have millisecond precision for the timestamps in the system log, for comparison of frame number values. Please enable CONFIG_PRINTK_TIME for the next test. 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>