On Mon, Jan 06, 2014 at 03:52:24PM +0000, David Laight wrote: > > From: Alan Stern > > Subject: Re: Bug#733826: crazy loop "xhci_hcd Too many fragments" > > > > On Mon, 6 Jan 2014, Ben Hutchings wrote: > > > > > On Sat, 2014-01-04 at 05:44 +0800, jidanni@xxxxxxxxxxx wrote: > ... > > > > # cat /var/log/syslog > > > > > > > > Jan 1 06:57:38 jidanni5 ntpd[2822]: Listen normally on 5 lo ::1 UDP 123 > > > > Jan 1 06:57:38 jidanni5 ntpd[2822]: Listen normally on 6 eth0 fe80::2289:84ff:fe28:ad9 UDP 123 > > > > Jan 1 06:57:38 jidanni5 ntpd[2822]: peers refreshed > > > > Jan 1 06:57:38 jidanni5 ntpd[2822]: Listening on routing socket on fd #23 for interface updates > > > > Jan 1 07:04:49 jidanni5 kernel: [ 559.624680] xhci_hcd 0000:00:14.0: Too many fragments 79, max > > 63 > > > > Jan 1 07:04:49 jidanni5 kernel: [ 559.624695] xhci_hcd 0000:00:14.0: Too many fragments 79, max > > 63 > > > > Jan 1 07:04:49 jidanni5 kernel: [ 559.624704] xhci_hcd 0000:00:14.0: Too many fragments 79, max > > 63 > > > > > > > > 100000 lines later... oops I mean an actual MILLION lines later > > > > > > Assuming my fix for the repetition is correct, the remaining problem is > > > why usb-storage is generating such large/fragmented urbs. > > > > usb-storage doesn't generate large or fragmented anything. It merely > > passes on the scatter-gather information it gets from the block layer. > > Although not a real fix to the underlying problem, it seems that the default > ring size is far too small. Did you mean ring segment size? > Any amount of network traffic also activates the ring expansion code. > IIRC each ring entry is 16 bytes, so increasing the ring size to 256 > still keeps the rings to a single 4k page. > > Whether anything regularly exceeds 255 fragments is a another matter. If so, yes, changing the segment size makes sense. TRBS_PER_SEGMENT could be increased to 256. I'm not sure if we should switch to using dma_alloc_coherent instead of a DMA pool. Some systems could be using bigger than 4K pages, so we should probably still stick with DMA pools. Ben, can you change your patch to increase TRBS_PER_SEGMENT to 256? Sarah Sharp -- 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
