On Fri, 22 May 2009 10:33:23 +0800 Wu Fengguang <fengguang.wu@xxxxxxxxx> wrote: > > I tested above patch, and I got same performance number. > > I wonder why if (PageUptodate(page)) check is there... > > Thanks! This is an interesting micro timing behavior that > demands some research work. The above check is to confirm if it's > the PageUptodate() case that makes the difference. So why that case > happens so frequently so as to impact the performance? Will it also > happen in NFS? > > The problem is readahead IO pipeline is not running smoothly, which is > undesirable and not well understood for now. The patch causes a remarkably large performance increase. A 9% reduction in time for a linear read? I'd be surprised if the workload even consumed 9% of a CPU, so where on earth has the kernel gone to? Have you been able to reproduce this in your testing? Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
