At 08:42 09/05/27, Andrew Morton wrote: >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 Hi Andrew. Yes, I tested this with dd. >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? Yes, this test on my environment is reproducible. 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
