>---------- Original message ---------- >From: Olof Johansson <[EMAIL PROTECTED]> >Date: Feb 14, 2008 3:38 AM >Subject: Dealing with limited resources and DMA Engine copies >To: [EMAIL PROTECTED], [EMAIL PROTECTED] >Cc: netdev@vger.kernel.org > >Hi, > >My DMA Engine has a limited resource: It's got a descriptor ring, so >it's not always possible to add a new descriptor to it (i.e. it might be >full). While allocating a huge ring will help, eventually I'm sure I >will hit a case where it'll overflow. > >I thought this was going to be taken care of automatically by the fact >that you return your max(?) number of descriptors in the channel >allocation function, but it looks like that value is discarded in >dma_client_chan_alloc(). > >So, I just got a couple of spurious: >dma_cookie < 0 >dma_cookie < 0 > >...on the console and the connection terminated. Looks like that came >from tcp_recvmsg(). Ouch. > >How about falling back to the cpu-based copy in case of failure? Or would >you prefer that I sleep locally in my driver and wait on a descriptor >slot to open up? >
I have taken a closer look at this in the code. It seems to be a good idea to withdraw for a while from ioat-dma copy in case of "dma_cookie < 0" error to let the ring free some descriptors. I will be able to work on it next week probably. As soon as I have some stable results, I will get back to you with it. Maciej --------------------------------------------------------------------- Intel Technology Poland sp. z o.o. z siedziba w Gdansku ul. Slowackiego 173 80-298 Gdansk Sad Rejonowy Gdansk Polnoc w Gdansku, VII Wydzial Gospodarczy Krajowego Rejestru Sadowego, numer KRS 101882 NIP 957-07-52-316 Kapital zakladowy 200.000 zl This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
