On Wed, May 27, 2009 at 08:25:04AM +0800, Hisashi Hifumi wrote: > > 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. Hisashi, does your environment have some special configurations? Thanks, Fengguang -- 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
