Date: Fri, 6 Jul 2018 12:44:48 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r336030 - head/sys/vm Message-ID: <201807061244.w66CimVq064290@repo.freebsd.org>
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Author: kib Date: Fri Jul 6 12:44:48 2018 New Revision: 336030 URL: https://svnweb.freebsd.org/changeset/base/336030 Log: Save a call to pmap_remove() if entry cannot have any pages mapped. Due to the way rtld creates mappings for the shared objects, each dso causes unmap of at least three guard map entries. For instance, in the buildworld load, this change reduces the amount of pmap_remove() calls by 1/5. Profiled by: alc Reviewed by: alc, markj Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D16148 Modified: head/sys/vm/vm_map.c Modified: head/sys/vm/vm_map.c ============================================================================== --- head/sys/vm/vm_map.c Fri Jul 6 12:37:46 2018 (r336029) +++ head/sys/vm/vm_map.c Fri Jul 6 12:44:48 2018 (r336030) @@ -3158,7 +3158,14 @@ vm_map_delete(vm_map_t map, vm_offset_t start, vm_offs if (entry->wired_count != 0) vm_map_entry_unwire(map, entry); - pmap_remove(map->pmap, entry->start, entry->end); + /* + * Remove mappings for the pages, but only if the + * mappings could exist. For instance, it does not + * make sense to call pmap_remove() for guard entries. + */ + if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0 || + entry->object.vm_object != NULL) + pmap_remove(map->pmap, entry->start, entry->end); /* * Delete the entry only after removing all pmap
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