> But all (both) the proposals we're (ahem) discussing do involve 4x > physically contiguous pages going into those four contiguous pagecache > slots. > > So we're improving things for the half-assed controllers, aren't we?
Not neccessarily. If you use 16K contiguous pages you have to do more work to get memory contiguously and you have less cache efficiency both of which will do serious damage to performance with poor I/O subsystems for all the extra paging and I/O, and probably way more than sglist stuff on PC class boxes. (yes its probably a win on your 32GB SGI monster) That aside you are improving things for most but not all half-assed controllers (some sglists are simply page pointers for each 4K page or have different efficient encoding for page sized chunks (I2O). If you are reading large chunks on a really crap controller (eg IDE in PIO) then the fact you pull 16K when you need 4K will also wipe out any gains. Alan - 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/
