On Thu, Aug 30, 2012 at 01:18:54PM +0100, Jonathan Tripathy wrote: > > On 30.08.2012 08:21, Jonathan Tripathy wrote: > >On 30/08/2012 08:15, Jonathan Tripathy wrote: > >>Hi There, > >> > >>On my WIndows DomU (Xen VM) which is running on a LV which is > >>using bcache (against two SSD in MDRAID1 and a MD-RAID10 spindle > >>array), I ran an IOMeter test for about 2 hours (with 30 workers > >>and a io depth of 256). This was a very heavy workload (Got an > >>average iops of about 6.5k). After I stopped the test, I then > >>went back to fio on my Linux Xen Host (Dom0). The random write > >>performance isn't as good as it was before I started the IOMeter > >>test. It used to be about 25k and now showed about 7k iops. I > >>assumed that maybe this was due to the fact that bcache was > >>writing out dirty data to the spindles so the SSD was busy. > >> > >>However, this morning, after the spindles have calmed down, > >>performance of fio is still not great (still about 7k). > >> > >>Is there something wrong here? What is expected behavior? > >> > >>Thanks > >> > >BTW, I can confirm that this isn't an SSD issue, as I have a > >partition on the SSD that I kept seperate from bcache and I'm getting > >excellent (about 28k) iops performance there. > > > >It's as if after the heavy workload I did with IOMeter, bcache has > >somehow throttled the writeback cache? > > > >Any help is appreciated. > > > > I'd like to add that a reboot pretty much solves the issue. This > leads me to believe that there is a bug in the bcache code that > causes performance to drop the more it gets used. > > Any ideas? Weird! Yeah, that definitely sounds like a bug. I'm going to have to try and reproduce it and go hunting. Can you think of anything that might help with reproducing it? -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
