On Wed, 2025-10-08 at 16:02 +0200, Christian König wrote: > On 08.10.25 15:50, Tvrtko Ursulin wrote: > > > > On 08/10/2025 13:35, Christian König wrote: > > > On 08.10.25 13:53, Tvrtko Ursulin wrote: > > > > Disclaimer: > > > > Please note that as this series includes a patch which touches > > > > a good number of > > > > drivers I will only copy everyone in the cover letter and the > > > > respective patch. > > > > Assumption is people are subscribed to dri-devel so can look at > > > > the whole series > > > > there. I know someone is bound to complain for both the case > > > > when everyone is > > > > copied on everything for getting too much email, and also for > > > > this other case. > > > > So please be flexible. > > > > > > > > Description: > > > > > > > > All drivers which use the TTM pool allocator end up requesting > > > > large order > > > > allocations when allocating large buffers. Those can be slow > > > > due memory pressure > > > > and so add latency to buffer creation. But there is often also > > > > a size limit > > > > above which contiguous blocks do not bring any performance > > > > benefits. This series > > > > allows drivers to say when it is okay for the TTM to try a bit > > > > less hard. > > > > > > > > We do this by allowing drivers to specify this cut off point > > > > when creating the > > > > TTM device and pools. Allocations above this size will skip > > > > direct reclaim so > > > > under memory pressure worst case latency will improve. > > > > Background reclaim is > > > > still kicked off and both before and after the memory pressure > > > > all the TTM pool > > > > buckets remain to be used as they are today. > > > > > > > > This is especially interesting if someone has configured > > > > MAX_PAGE_ORDER to > > > > higher than the default. And even with the default, with amdgpu > > > > for example, > > > > the last patch in the series makes use of the new feature by > > > > telling TTM that > > > > above 2MiB we do not expect performance benefits. Which makes > > > > TTM not try direct > > > > reclaim for the top bucket (4MiB). > > > > > > > > End result is TTM drivers become a tiny bit nicer mm citizens > > > > and users benefit > > > > from better worst case buffer creation latencies. As a side > > > > benefit we get rid > > > > of two instances of those often very unreadable mutliple > > > > nameless booleans > > > > function signatures. > > > > > > > > If this sounds interesting and gets merge the invidual drivers > > > > can follow up > > > > with patches configuring their thresholds. > > > > > > > > v2: > > > > * Christian suggested to pass in the new data by changing the > > > > function signatures. > > > > > > > > v3: > > > > * Moved ttm pool helpers into new ttm_pool_internal.h. > > > > (Christian) > > > > > > Patch #3 is Acked-by: Christian König <[email protected]>. > > > > > > The rest is Reviewed-by: Christian König > > > <[email protected]> > > > > Thank you! > > > > So I think now I need acks to merge via drm-misc for all the > > drivers which have their own trees. Which seems to be just xe. > > I think you should ping the XE guys for their opinion, but since > there shouldn't be any functional change for them you can probably go > ahead and merge the patches to drm-misc-next when there is no reply > in time.
I will try to do a review tonight. One thing that comes up though, is the change to ttm_device_init() where you add pool_flags. I had another patch series a number of months ago that added a struct with flags there instead to select the return value given when OOM. Now that we're adding an argument, should we try to use a struct instead so that we can use it for more that pool behavior? I'll be able to find a pointer to that series later today. /Thomas
