On mercoledì 21 giugno 2023 11:06:51 CEST Thomas Hellström (Intel) wrote: > > I think one thing worth mentioning in the context of this patch is that > IIRC kmap_local_page() will block offlining of the mapping CPU until > kunmap_local(), Migration is disabled. > so while I haven't seen any guidelines around the usage > of this api for long-held mappings, It would be advisable to not use it for long term mappings, if possible. These "local" mappings should better be help for not too long duration. > I figure it's wise to keep the > mapping duration short, or at least avoid sleeping with a > kmap_local_page() map active. Nothing prevents a call of preempt_disable() around the section of code between kmap_local_page() / kunmap_local(). If it is needed, local mappings could also be acquired under spinlocks and/or with disabled interrupts. I don't know the code, however, everything cited above could be the subject of a subsequent patch. Regards, Fabio > I figured, while page compression is probably to be considered "slow" > it's probably not slow enough to motivate kmap() instead of > kmap_local_page(), but if anyone feels differently, perhaps it should be > considered. > > With that said, my Reviewed-by: still stands. > > /Thomas >
