2009/7/8 Vladislav Bolkhovitin <vst@xxxxxxxx>: > Ronald Moesbergen, on 07/08/2009 12:49 PM wrote: >> >> 2009/7/7 Vladislav Bolkhovitin <vst@xxxxxxxx>: >>> >>> Ronald Moesbergen, on 07/07/2009 10:49 AM wrote: >>>>>>> >>>>>>> I think, most likely, there was some confusion between the tested and >>>>>>> patched versions of the kernel or you forgot to apply the io_context >>>>>>> patch. >>>>>>> Please recheck. >>>>>> >>>>>> The tests above were definitely done right, I just rechecked the >>>>>> patches, and I do see an average increase of about 10MB/s over an >>>>>> unpatched kernel. But overall the performance is still pretty bad. >>>>> >>>>> Have you rebuild and reinstall SCST after patching kernel? >>>> >>>> Yes I have. And the warning about missing io_context patches wasn't >>>> there during the compilation. >>> >>> Can you update to the latest trunk/ and send me the kernel logs from the >>> kernel's boot after one dd with any block size you like >128K and the >>> transfer rate the dd reported, please? >>> >> >> I think I just reproduced the 'wrong' result: >> >> dd if=/dev/sdc of=/dev/null bs=512K count=2000 >> 2000+0 records in >> 2000+0 records out >> 1048576000 bytes (1.0 GB) copied, 12.1291 s, 86.5 MB/s >> >> This happens when I do a 'dd' on the device with a mounted filesystem. >> The filesystem mount causes some of the blocks on the device to be >> cached and therefore the results are wrong. This was not the case in >> all the blockdev-perftest run's I did (the filesystem was never >> mounted). > > Why do you think the file system (which one, BTW?) has any additional > caching if you did "echo 3 > /proc/sys/vm/drop_caches" before the tests? All > block devices and file systems use the same cache facilities. I didn't drop the caches because I just restarted both machines and thought that would be enough. But because of the mounted filesystem the results were invalid. (The filesystem is OCFS2, but that doesn't matter). > I've also long ago noticed that reading data from block devices is slower > than from files from mounted on those block devices file systems. Can > anybody explain it? > > Looks like this is strangeness #2 which we uncovered in our tests (the first > one was earlier in this thread why the context RA doesn't work with > cooperative I/O threads as good as it should). > > Can you rerun the same 11 tests over a file on the file system, please? I'll see what I can do. Just te be sure: you want me to run blockdev-perftest on a file on the OCFS2 filesystem which is mounted on the client over iScsi, right? Ronald. -- 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
