On Fri, 2009-07-10 at 16:17 +0800, Wu Fengguang wrote: > On Fri, Jul 10, 2009 at 03:41:54PM +0800, Zhang, Yanmin wrote: > > On Fri, 2009-07-10 at 14:37 +0800, Wu Fengguang wrote: > > > On Tue, Jul 07, 2009 at 02:06:42PM +0800, Zhang, Yanmin wrote: > > > > On Tue, 2009-07-07 at 02:01 +0200, Rafael J. Wysocki wrote: > > > > > This message has been generated automatically as a part of a report > > > > > of recent regressions. > > > > > > > > > > The following bug entry is on the current list of known regressions > > > > > from 2.6.30. Please verify if it still should be listed and let me know > > > > > (either way). > > > > > > > > > > > > > > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=13726 > > > > > Subject : fio sync read 4k block size 35% regression > > > > > Submitter : Zhang, Yanmin <yanmin_zhang@xxxxxxxxxxxxxxx> > > > > > Date : 2009-07-01 11:25 (6 days old) > > > > > First-Bad-Commit: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=51daa88ebd8e0d437289f589af29d4b39379ea76 > > > > > References : http://lkml.org/lkml/2009/6/30/679 > > > > > Handled-By : Wu Fengguang <fengguang.wu@xxxxxxxxx> > > > > Fengguang, > > > > > > > > I'm still working on it now. The new testing against 2.6.31-rc2 is ongoing. > > > > fio sync/mmap read has new behavior. I did collect some data. But suddenly > > > > with new created data, the fio_sync_read_4k regression disappeared, while > > > > > > Do you mean the fio_sync_read_4k regression disappeared because we are > > > collecting data with lots of printks? > > No. I recreated the data and the regression disappeared. > > OK. It's because you recreated the files, instead of upgrading to -rc2? Yes. > > > > > > > > fio_mmap_read is still there. Originally, the testing and bisect were stable. > > > > Let me check what happens firstly. > > > > > > Thanks! What's your fio_mmap_read job file and the readahead traces? > > I dumped trace data of fio and found the sync read isn't really sequential. I > > create many processes and every process could read a group of files. The trace > > shows fio reads a record of a file, then switch to another file to read. My > > original assumption is a process reads the complete file sequentially and then > > read the 2nd file. Now I upgrade fio the latest version and add parameter > > file_service_type=random:4000000 to rerun all testing. > > However you organize the workload, it is a regression. If you mean > "this workload is expected to create regressions", then let's improve > the algorithm to cover that workload? Thanks Fengguang. You work carefully and be ready to resolve any regression. When creating the workloads, I try to simulate _RealUsageModels_. For example, fio_mmap_sync_read and fio_sync_read are to simulate ftp/web server and media player to download big files. Such workloads mostly read files sequentially, not interspersally among many files. I also have other workloads, such like fio_mmap_rand_read/write simulating small/medium databases, which need IO interspersally among a coulpe of files. As for this report, my original testing reads files interspersally. It's hard to find the usage models. In other hand, sometimes a method to improve one workload might hurt other workloads. So let's focus on good workloads. With the latest version of fio and new parameters, I found some other regressions. I will check them and report if necessary. > > In your previous workload, what's the exact read pattern for any > single file over time? Sequential read, but read a block (4k64k/128k), then switch to next file to read another block. As for single file, read sequentially. If there are 3 files: 1) read 1st block of f1; then read 1st block of f2; then f3; 2) read 2nd block of f1; then read 2nd block of f2; then f3; 3) ... Such read scenario isn't good. I created it incorrectly because I misunderstood some parameters of fio. Pls. close the report. yanmin -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
