On Mon, Jul 23 2007, Jörn Engel wrote: > On Sun, 22 July 2007 18:44:03 +0200, Jens Axboe wrote: > > > > > > > I agree with the low point of 128k. > > > > > > Perhaps that should be enforced then, because currently a system with > > > <64M will get less. > > > > I think it should remain the low point. > > I believe this whole thing is fundamentally flawed. The perfect > readahead size depends on the device in question. If we set a single > system-wide value depending on memory size, it may easily be too small > and too large at the same time. Think hard disk and SSD. > > It may make sense to have a _maximum_ readahead size which depends on > memory size. But the preferred size (if there is enough RAM) should > depend solely on the device, possibly as a function of the > bandwidth * read latency product.
The value IS the maximum read-ahead value, not an enforced minimum. However, there's definitely room for improvement in the queue feedback. Even for seekless devices like SSD, read-ahead may be beneficial due to zero request -> request latency. -- 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/
