On Wed, 02 Mar 2005 01:08:56 -0500, Jeff Garzik <[EMAIL PROTECTED]> wrote: > Bartlomiej Zolnierkiewicz wrote: > > Yes but it seems that you've assumed that ioctl == flagged taskfile > > and fs/internal == normal taskfile which is _not_ what I aim for. > > > > I want fully-flagged taskfile handling like flagged_taskfile() and "hot > > path" > > simpler taskfile handling like do_rw_taskfile() (at least for now - we can > > remove "hot path" later) where both can be used for fs/internal/ioctl > > requests > > (depending on the flags). > > There is no effective difference in performance between > > writeb() > writeb() > writeb() > writeb() > > and > > if (bit 1) > writeb() > if (bit 2) > writeb() > if (bit 3) > writeb() > if (bit 4) > writeb() > > The cost of a repeated bit test on the same unsigned long is _zero_. > It's already in L1 cache. The I/Os are slow, and adding bit tests will
certainly it is not _zero_ ;-) I agree that it is negligible compared to the cost of I/O > not measurably decrease performance. (this is the reason why I do not > object to using ioread32() and iowrite32()... it just adds a simple test) > > Plus, it is better to have a single path for all taskfiles, to ensure > that the path is well-tested. > > libata's ->tf_load() and ->tf_read() hooks should be updated to use the > more fine-grained flags that Tejun is proposing. > > Note that on SATA, this is largely irrelevant. The functions > ata_tf_read() and ata_tf_load() should be updated for flagged taskfiles, > because these will be used with PATA drivers. > > The hooks implemented in individual SATA drivers will not be updated. > The reason is that SATA transmits an entire copy of the taskfile to/from > the device all at once, in the form of a Frame Information Structure > (FIS) -- essentially a SATA packet. agreed Tejun, one-path approach for IDE driver is fine with me - 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/
