On Fri, 2025-10-10 at 16:11 +0200, Thomas Hellström wrote: > On Thu, 2025-10-09 at 09:53 +0100, Tvrtko Ursulin wrote: > > > > On 08/10/2025 15:39, Thomas Hellström wrote: > > > 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. > > > > Found it: > > https://lore.kernel.org/dri-devel/[email protected]/ > > > > Glad to see in that thread it isn't just me permanently slowed down > > by > > "false, false" and similar. :) > > > > I considered using a struct too and I guess there wasn't too much > > of > > a > > sway that I went with flags. I thought not to overcomplicate with > > the > > on > > stack struct which is mostly not needed for something so low level, > > and > > to stick with the old school C visual patterns. > > > > Since you only needed a single boolean in your series I suppose you > > could just follow up on my series if you find it acceptable. Or I > > can > > go > > with yours, no problem either. > > It seems yours has the most momentum ATM. I can follow up on yours. > It > would be great if we could perhaps change the naming of "pool_flags" > to > something more generic.
Oh, BTW we started using that 'const struct' flags argument style in xe and in the TTM shrinker helper (ttm_bo_shrink()) as well, so there is a precedent. I'll let you decide :) Thanks, Thomas > > Thanks, > Thomas > > > > > > Regards, > > > > Tvrtko > > >
