Messages in this thread | | | Date | Tue, 23 Oct 2001 20:10:10 +0200 | From | Jens Axboe <> | Subject | Re: [Lse-tech] Re: Preliminary results of using multiblock raw I/O |
| |
On Tue, Oct 23 2001, Shailabh Nagar wrote: > >On Tue, Oct 23 2001, Martin Frey wrote: > >> >I haven't seen the SGI rawio patch, but I'm assuming it used kiobufs to > >> >pass a single unit of 1 meg down at the time. Yes currently we do incur > >> >significant overhead compared to that approach. > >> > > >> Yes, it used kiobufs to get a gatherlist, setup a gather DMA out > >> of that list and submitted it to the SCSI layer. Depending on > >> the controller 1 MB could be transfered with 0 memcopies, 1 DMA, > >> 1 interrupt. 200 MB/s with 10% CPU load was really impressive. > > > >Let me repeat that the only difference between the kiobuf and the > >current approach is the overhead incurred on multiple __make_request > >calls. Given the current short queues, this isn't as bad as it used to > >be. Of course it isn't free, though. > > The patch below attempts to address exactly that - reducing the number of > submit_bh/__make_request() calls made for raw I/O. The basic idea is to do > a major > part of the I/O in page sized blocks. > > Comments on the idea ?
Looks fine to me.
-- Jens Axboe
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |