On 29/11/16 22:01 +0200, Yaniv Kaul wrote:
It appears that VDSM changes the following params: vm.dirty_ratio = 5 vm.dirty_background_ratio = 2
Any idea why? Because we use cache=none it's irrelevant anyway?
It's not really irrelevant, the host still uses disk cache. Anyway, there is BZ[1] with a presentation[2] that (imho reasonably) states: "Reduce dirty page limits in KVM host to allow direct I/O writer VMs to compete successfully with buffered writer processes for storage access" I wonder why virtual-host tuned profile doesn't contain these values: $ grep vm.dirty /usr/lib/tuned/virtual-host/tuned.conf vm.dirty_background_ratio = 5 [1]https://bugzilla.redhat.com/show_bug.cgi?id=740887 [2]http://perf1.lab.bos.redhat.com/bengland/laptop/rhev/rhev-vm-rsptime.pdf
TIA, Y.
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