On Wed, 27 May 2009 11:21:53 +0900 Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx> wrote: > > 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. > Ah. So it's likely to be some strange interaction with the RAID setup. I assume that you're using the SANNet 2's "hardware raid"? Or is the array set up as jbod and you're using kernel raid0? -- 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
