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3a8247cc2c
At present, if we have a kernel with a 64kB page size, and some process maps something that has to be mapped with 4kB pages (such as a cache-inhibited mapping on POWER5+, or the eHCA infiniband queue-pair pages), we change the process to use 4kB pages everywhere. This hurts the performance of HPC programs that access eHCA from userspace. With this patch, the kernel will only demote the slice(s) containing the eHCA or cache-inhibited mappings, leaving the remaining slices able to use 64kB hardware pages. This also changes the slice_get_unmapped_area code so that it is willing to place a 64k-page mapping into (or across) a 4k-page slice if there is no better alternative, i.e. if the program specified MAP_FIXED or if there is not sufficient space available in slices that are either empty or already have 64k-page mappings in them. Signed-off-by: Paul Mackerras <paulus@samba.org> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
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