At 11:09 09/05/27, Wu Fengguang wrote: >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? Hi. My testing environment is as follows: Hardware: HP DL580 CPU:Xeon 3.2GHz *4 HT enabled Memory:8GB Storage: Dothill SANNet2 FC (7Disks RAID-0 Array) I did dd to this disk-array and got improved performance number. I noticed that when a disk is just one HDD, performance improvement is very small. 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
