On Wed, Mar 17, 2021 at 2:33 AM Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx> wrote: > > Hi Rob, > > On 2021-03-16 22:46, Rob Clark wrote: > > <snip>... > > >> > > > >> > > When the GPU has a buffer mapped with IOMMU_LLC, is the buffer also mapped > >> > > into the CPU and with what attributes? Rob said "writecombine for > >> > > everything" -- does that mean ioremap_wc() / MEMREMAP_WC? > >> > > >> > Currently userspace asks for everything WC, so pgprot_writecombine() > >> > > >> > The kernel doesn't enforce this, but so far provides no UAPI to do > >> > anything useful with non-coherent cached mappings (although there is > >> > interest to support this) > >> > > >> > >> btw, I'm looking at a benchmark (gl_driver2_off) where (after some > >> other in-flight optimizations land) we end up bottlenecked on writing > >> to WC cmdstream buffers. I assume in the current state, WC goes all > >> the way to main memory rather than just to system cache? > >> > > > > oh, I guess this (mentioned earlier in thread) is what I really want > > for this benchmark: > > > > https://android-review.googlesource.com/c/kernel/common/+/1549097/3 > > > > You can also check if the system cache lines are allocated for GPU > or not with patch in https://crrev.com/c/2766723 > > With the above patch applied, > cat /sys/kernel/debug/llcc_stats/llcc_scid_status > > The SCIDs for GPU are listed in include/linux/soc/qcom/llcc-qcom.h > Actually for the benchmark I was referring to, it is the *CPU* bottlenecked on writes to writecombine mappings.. so I think what I want is for CPU mappings to be able to use systemcache.. BR, -R _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
