On Sun, Aug 28 2005, Arjan van de Ven wrote: > On Sun, 2005-08-28 at 05:42 -0400, Jeff Garzik wrote: > > The constant ATA_SHT_USE_CLUSTERING in include/linux/libata.h controls > > the use of SCSI layer's use_clustering feature, for a great many libata > > drivers. > > > > The current setup has clustering disabled, which in theory causes the > > block layer to do less work, at the expense of a greater number of > > scatter/gather table entries used. > > > > Any opinions WRT turning on clustering for libata? > > in 2.4 clustering was expensive due to a large number of checks that > were done (basically the number of fragments got recounted a gazilion > times). In 2.6 Jens fixed that afaik to make it basically free... > at which point it's a win always. Yeah, it wont cost any extra cycles, so there's no point in keeping it turned off for that reason. > Imo clustering on the driver level should announce driver capabilities. > If clustering for some arch/kernel makes it slower, that should be > decided at a midlayer level and not in each driver; eg the midlayer > would chose to ignore the drivers capabilities. > So .. my opinion would be that libata should announce the capability (it > seems the code/hw can do it). Agree, we should just remove the ability to control clustering, as it really overlaps with the segment settings anyways. -- Jens Axboe - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
