On Mon, Mar 05, 2007 at 09:20:10AM -0600, Joel Schopp wrote: > >But if you don't require a lot of higher order allocations anyway, then > >guest fragmentation caused by ballooning doesn't seem like much problem. > > If you only need to allocate 1 page size and smaller allocations then no > it's not a problem. As soon as you go above that it will be. You don't > need to go all the way up to MAX_ORDER size to see an impact, it's just > increasingly more severe as you get away from 1 page and towards MAX_ORDER.
We allocate order 1 and 2 pages for stuff without too much problem. > >If you need higher order allocations, then ballooning is bad because of > >fragmentation, so you need memory unplug, so you need higher order > >allocations. Goto 1. > > Yes, it's a closed loop. But hotplug isn't the only one that needs higher > order allocations. In fact it's pretty far down the list. I look at it > like this, a lot of users need high order allocations for better > performance and things like on-demand hugepages. As a bonus you get memory > hot-remove. on-demand hugepages could be done better anyway by having the hypervisor defrag physical memory and provide some way for the guest to ask for a hugepage, no? > >Balooning probably does skew memory management stats and watermarks, but > >that's just because it is implemented as a module. A couple of hooks > >should be enough to allow things to be adjusted? > > That is a good idea independent of the current discussion. Well it shouldn't be too difficult. If you cc linux-mm and/or me with any thoughts or requirements then I could try to help with it. Thanks, Nick - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
