On lunedì 27 marzo 2023 15:23:41 CEST Matthew Wilcox wrote: > On Mon, Mar 27, 2023 at 12:13:08PM +0200, Fabio M. De Francesco wrote: > > On giovedì 29 dicembre 2022 23:50:56 CEST Fabio M. De Francesco wrote: > > > kmap() is being deprecated in favor of kmap_local_page(). > > > > > > There are two main problems with kmap(): (1) It comes with an overhead as > > > the mapping space is restricted and protected by a global lock for > > > synchronization and (2) it also requires global TLB invalidation when the > > > kmap’s pool wraps and it might block when the mapping space is fully > > > utilized until a slot becomes available. > > > > > > With kmap_local_page() the mappings are per thread, CPU local, can take > > > page faults, and can be called from any context (including interrupts). > > > It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, > > > the tasks can be preempted and, when they are scheduled to run again, the > > > kernel virtual addresses are restored and still valid. > > > > > > Since its use in fs/ufs is safe everywhere, it should be preferred. > > > > > > Therefore, replace kmap() with kmap_local_page() in fs/ufs. kunmap_local() > > > requires the mapping address, so return that address from ufs_get_page() > > > to be used in ufs_put_page(). > > > > Hi Al, > > > > I see that this series is here since Dec 29, 2022. > > Is there anything that prevents its merging? > > Can you please its four patches in your tree? > > I'm pretty sure UFS directories should simply be allocated from lowmem. > There's really no reason to put them in highmem these days. Matthew, It's been a few days since you wrote but I still haven't done anything or replied. For now, I just want you to know that it's not my intention to ignore your comment. The only reasons I hesitate to follow your directions are that I built this series based on specific suggestions from Al. While I understand and, for sure, heed what you said, I also think I should wait for Al to chime in with what he thinks about all this before taking a different route for removing kmap() from fs/ufs. Thanks for looking at this series. Fabio
