On Thu, 14 Feb 2008 11:34:03 -0700 "Dan Williams" <[EMAIL PROTECTED]> wrote:
> On Thu, Feb 14, 2008 at 1:36 AM, Haavard Skinnemoen > <[EMAIL PROTECTED]> wrote: > > It's ok to use PIO for small and/or odd transfers like "read 2 bytes > > from this SDIO register", something that the mmc-block driver would > > never ask us to do. Using PIO for huge block data transfers will really > > hurt. > > Except your testing has already shown that running out of descriptors > rarely, if ever happens. It just becomes an exercise in tuning the > pool size, and letting this simple fall back mechanism be a safety net > for the corner cases. True...it's just that you normally expect _better_ performance when increasing the size of the transfer. I'm just afraid that someone might start tuning things elsewhere, only to find that crossing a certain threshold gives a drastic reduction in performance. That would be completely counter-intuitive. > > I think I'll try triggering the mmc tasklet from the DMA callback for > > now. Scheduling a tasklet from another tasklet should work just fine, > > right? > > Yeah that should work because you are no longer under the channel lock. Right. And if we insert the interrupt descriptor somewhere in the middle instead of at the end, we should be able to submit a new batch of descriptors before the previous batch is exhausted, thus maintaining maximum throughput without any pauses. I'll probably keep it simple at first though. Gotta save some optimizations for later ;) Haavard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
