At 11:37 09/06/01, Wu Fengguang wrote: >On Wed, May 27, 2009 at 11:06:37AM +0800, Hisashi Hifumi wrote: >> >> At 11:57 09/05/27, Wu Fengguang wrote: >> >On Wed, May 27, 2009 at 10:47:47AM +0800, Hisashi Hifumi wrote: >> >> >> >> At 11:36 09/05/27, Wu Fengguang wrote: >> >> >On Wed, May 27, 2009 at 10:21:53AM +0800, Hisashi Hifumi 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) >> >> > >> >> >This is a big hardware RAID. What's the readahead size? >> >> > >> >> >The numbers look too small for a 7 disk RAID: >> >> > >> >> > > #dd if=testdir/testfile of=/dev/null bs=16384 >> >> > > >> >> > > -2.6.30-rc6 >> >> > > 1048576+0 records in >> >> > > 1048576+0 records out >> >> > > 17179869184 bytes (17 GB) copied, 224.182 seconds, 76.6 MB/s >> >> > > >> >> > > -2.6.30-rc6-patched >> >> > > 1048576+0 records in >> >> > > 1048576+0 records out >> >> > > 17179869184 bytes (17 GB) copied, 206.465 seconds, 83.2 MB/s >> >> > >> >> >I'd suggest you to configure the array properly before coming back to >> >> >measuring the impact of this patch. >> >> >> >> >> >> I created 16GB file to this disk array, and mounted to testdir, dd to >> >this directory. >> > >> >I mean, you should get >300MB/s throughput with 7 disks, and you >> >should seek ways to achieve that before testing out this patch :-) >> >> Throughput number of storage array is very from one product to another. >> On my hardware environment I think this number is valid and >> my patch is effective. > >What's your readahead size? Is it large enough to cover the stripe width? Do you mean strage's readahead size? -- 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
