On Monday, December 12, 2016 at 7:22:39 PM UTC+1, Chris Laprise wrote: > > Just wanted to note there are various warnings against using > swappiness=0 as it can result in killed processes; swappiness=1 is > considered the minimum value to avoid this problem. > > > https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Performance_Tuning_Guide/s-memory-tunables.html > > https://en.wikipedia.org/wiki/Swappiness > > Chris >
Not nice. So, IIUC, * we should have vm.swappiness=1 instead of vm.swappiness=0 * we should consider the (even tiny) swappiness in reasoning about the formula for required/assigned memory. So, having enough memory that do not reach swappiness watermark requires multiplying the memory by 1/(1-swappiness/100). This might play well for swappiness=1 (factor 1.01, i.e. just 1% overhead), but it sounds strange (and counterproductive) for swappiness=50 (factor 2, i.e. 100% overhead). So, when we have a memory requirements calculation function (In my previous post, I suggested f(req) = req + max(50, min(400, 0.3*req)) MiB, but I don't insist on this one), there are two variants: a) Simple variant: Assume that there is no use case for large vm.swappiness in Qubes: f(usage_mem)/(1-swappiness/100) b) Complex variant: Assume one might want higher swappiness, so add some upper limit: min(f(usage_mem+usage_swap), f(usage_mem)/(1-swappiness/100)) Does this sound reasonable? Regards, Vít Šesták 'v6ak' -- You received this message because you are subscribed to the Google Groups "qubes-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-devel+unsubscr...@googlegroups.com. To post to this group, send email to qubes-devel@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-devel/fe518af9-d9cb-497e-aecc-7ae56e6fc9d8%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
