On Thursday, February 6, 2020 at 12:23:47 PM UTC-7, Jan Kiszka wrote: > On 06.02.20 20:15, Michael Hinton wrote: > > Hi Jan, > > > > On Thursday, February 6, 2020 at 12:06:05 PM UTC-7, Jan Kiszka wrote: > > > > On 06.02.20 20:00, Michael Hinton wrote: > > > map_range((char *)MGH_HEAP_BASE, MGH_HEAP_SIZE, MAP_UNCACHED); > > > > Why are you mapping your RAM uncached? That's (roughly) only needed > for > > MMIO. > > > > > > > I see that it sets the PG_PCD argument to the page table entry in > > map_range(). What does that do? > > That controls caching on page-level granularity. > > > > > Should I set it to MAP_UNCACHED and see if that helps with performance? > > MAP_CACHED. When it's uncached, every memory access will hit the RAM. > That is... not very fast. > > Jan >
Switching to MAP_CACHED worked! My inmate now runs 100 ms faster than the same workload in the root cell. The inmate went from 2.8 s down to 1.1 seconds with that change. > I guess I was copying the other map_range() call used to set up the > > IVSHMEM from the ivshmem demo. So I have no particular reason. > The ivshmem demo is doing that only for the MMIO register region, not > the shared memory is later maps. Running the workload directly on input in shared memory with IVSHMEM is super slow, so I'm wondering if the data portion is indeed UNCACHED, contrary to what you say. Or maybe there is some other bottleneck. I will try to investigate that some more (maybe I will change it to CACHED as well and see what happens). But at any rate, for my purposes, I can always copy the data out of IVSHMEM into the cached memory region for now now. Thanks, Michael > -- > Siemens AG, Corporate Technology, CT RDA IOT SES-DE > Corporate Competence Center Embedded Linux > -- You received this message because you are subscribed to the Google Groups "Jailhouse" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/jailhouse-dev/8c4969cc-6165-42bb-9647-b19966635742%40googlegroups.com.
