On Thu, Mar 21, 2013 at 06:04:59PM +0100, Soeren Moch wrote: > On 03/17/13 18:36, 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. > > > > Now I found out what is going on here: > > In itd_urb_transaction() we allocate 9 iTDs for each URB with > number_of_packets == 64 in my case. The iTDs are added to > sched->td_list. For a frame-aligned scheduling we need 8 iTDs, the > 9th one is released back to the front of the streams free_list in > iso_sched_free(). This iTD was cleared after allocation and has a > frame number of 0 now. So for each allocation when now_frame == 0 we > allocate from the dma_pool, not from the free_list. The attached > patch invalidates the frame number in each iTD before it is sent to > the scheduler. This fixes the problem without the need to iterate > over a iTD list. > > Signed-off-by: Soeren Moch <smoch@xxxxxx> Wow! Great work Soeren! Talk about a long road to a small fix. Thanks for keeping after it. thx, Jason. > > > > --- linux-3.9.0-rc3-guru/drivers/usb/host/ehci-sched.c.orig 2013-03-21 17:36:21.000000000 +0100 > +++ linux-3.9.0-rc3-guru/drivers/usb/host/ehci-sched.c 2013-03-21 17:38:56.000000000 +0100 > @@ -1214,6 +1214,7 @@ itd_urb_transaction ( > > memset (itd, 0, sizeof *itd); > itd->itd_dma = itd_dma; > + itd->frame = -1; > list_add (&itd->itd_list, &sched->td_list); > } > spin_unlock_irqrestore (&ehci->lock, flags); > @@ -1915,6 +1916,7 @@ sitd_urb_transaction ( > > memset (sitd, 0, sizeof *sitd); > sitd->sitd_dma = sitd_dma; > + sitd->frame = -1; > list_add (&sitd->sitd_list, &iso_sched->td_list); > } > -- 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>