On Friday 08 May 2009, Jesse Barnes wrote: > On Fri, 08 May 2009 09:32:34 +1000 > Nigel Cunningham <nigel@xxxxxxxxxxxx> wrote: > > > Hi. > > > > On Thu, 2009-05-07 at 16:14 -0700, Jesse Barnes wrote: > > > On Fri, 08 May 2009 06:41:00 +1000 > > > Nigel Cunningham <nigel@xxxxxxxxxxxx> wrote: > > > > > > > Hi. > > > > > > > > On Thu, 2009-05-07 at 21:27 +0200, Rafael J. Wysocki wrote: > > > > > In fact I agree, but there's a catch. The way in which TuxOnIce > > > > > operates LRU pages is based on some assumptions that may or may > > > > > not be satisfied in future, so if we decide to merge it, then > > > > > we'll have to make sure these assumptions will be satisfied. > > > > > That in turn is going to require quite some discussion I guess. > > > > > > > > Agreed. That's why I've got that GEMS patch - it's putting pages > > > > on the LRU that don't satisfy the former assumptions: they are > > > > used during hibernating and need to be atomically copied. If > > > > there are further developments in that area, I would hope we > > > > could just extend what's been done with GEMS. > > > > > > Another option here would be to suspend all DRM operations earlier. > > > The suspend hook for i915 already does this, but maybe it needs to > > > happen sooner? We'll probably want a generic DRM suspend hook soon > > > too (as the radeon memory manager lands) to shut down GPU activity > > > in the suspend and hibernate cases. > > > > > > All that assumes I understand what's going on here though. :) It > > > appears you delay saving the GEM (just GEM by the way, for > > > Graphics/GPU Execution Manager) backing store until late to avoid > > > having the pages move around out from under you? > > > > Yeah. TuxOnIce saves some pages without doing an atomic copy of them. > > Up 'til now, the algorithm has been LRU pages - pages used for > > TuxOnIce's userspace helpers. With GEM, we also need to make sure GEM > > pages are atomically copied and so also 'subtract' them from the list > > of pages that aren't atomically copied. > > > > It's no great problem to do this, so I wouldn't ask you to change GEM > > to suspend DRM operations earlier. It's more important that GEM > > doesn't allocate extra pages unexpectedly - and I don't think that's > > likely anyway since we've switched away from X. This is important > > because TuxOnIce depends (for reliability) on having memory usage > > being predictable much more than swsusp and uswsusp do. (Larger > > images, less free RAM to begin with). > > Yeah X is typically the one causing GEM allocations and performing > execution, but there are other possibilities too. E.g. Wayland is a > non-X based display system that may be running instead, or maybe > there's an EGL or GPGPU program running in the background. > > So I think it's best if we suspend DRM fairly early, otherwise you > *may* get extra allocations and will probably see all sorts of GPU > memory mapping activity and execution while you're trying to hibernate > things. On the plus side I don't think this is a radical redesign or > anything, and mostly something we can do in our suspend and hibernate > callbacks. I think hibernate callbacks are too late for that. PM notifiers, OTOH, are probably too early. So, I really think we'll need to do something special about it. Thanks, Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
