On Fri, Aug 31 2007, Christoph Lameter wrote: > On Fri, 31 Aug 2007, Jens Axboe wrote: > > > > Ok. So another solution maybe to limit the blocksizes that can be used > > > with a device? > > > > That'd work for creation, but not for moving things around. > > What do you mean by moving things around? Creation binds a filesystem to a > device.
Only the bottom part. Change controller, move disk, whatever. There are lots of ways to change part of the IO path. > > > Hmmmm.. We could keep the existing scheme too and check that device > > > drivers split things up if they are too large? Isnt it possible today > > > to create a huge bio of 2M for huge pages and send it to a device? > > > > Not sure, aren't the constituents of compound pages the basis for IO? > > get_user_pages() serializes compound pages into the base pages. But doesnt > the I/O layer coalesce these later into 2M chunks again? You pretty much hit the nail on the head there yourself. The io layer _may_ coalesce them all together, but it may also stop at am arbitrary point and put the remainder in another request. This situation is different from submitting one huge piece, the above is what has always happened regardless of whether the origin happens to be a compound page or not. -- Jens Axboe - 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/
