From 93bd5b27d226cdd0bdc203a78e10dcacc11e2329 Mon Sep 17 00:00:00 2001 From: alc Date: Thu, 1 Dec 2016 17:26:37 +0000 Subject: [PATCH] During vm_page_cache()'s call to vm_radix_insert(), if vm_page_alloc() was called to allocate a new page of radix trie nodes, there could be a call to vm_radix_remove() on the same trie (of PG_CACHED pages) as the in-progress vm_radix_insert(). With the removal of PG_CACHED pages, we can simplify vm_radix_insert() and vm_radix_remove() by removing the flags on the root of the trie that were used to detect this case and the code for restarting vm_radix_insert() when it happened. Reviewed by: kib, markj Tested by: pho Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D8664 --- sys/vm/_vm_radix.h | 4 ---- sys/vm/vm_object.c | 1 - sys/vm/vm_radix.c | 57 ++-------------------------------------------- 3 files changed, 2 insertions(+), 60 deletions(-) diff --git a/sys/vm/_vm_radix.h b/sys/vm/_vm_radix.h index 1d06d0aac26c..f06646240b2a 100644 --- a/sys/vm/_vm_radix.h +++ b/sys/vm/_vm_radix.h @@ -36,12 +36,8 @@ */ struct vm_radix { uintptr_t rt_root; - uint8_t rt_flags; }; -#define RT_INSERT_INPROG 0x01 -#define RT_TRIE_MODIFIED 0x02 - #ifdef _KERNEL static __inline boolean_t diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c index 676a6971f321..df27e0c9ca4e 100644 --- a/sys/vm/vm_object.c +++ b/sys/vm/vm_object.c @@ -205,7 +205,6 @@ vm_object_zinit(void *mem, int size, int flags) object->type = OBJT_DEAD; object->ref_count = 0; object->rtree.rt_root = 0; - object->rtree.rt_flags = 0; object->paging_in_progress = 0; object->resident_page_count = 0; object->shadow_count = 0; diff --git a/sys/vm/vm_radix.c b/sys/vm/vm_radix.c index 4b1735794448..14f2f6e38cee 100644 --- a/sys/vm/vm_radix.c +++ b/sys/vm/vm_radix.c @@ -341,8 +341,6 @@ vm_radix_insert(struct vm_radix *rtree, vm_page_t page) index = page->pindex; -restart: - /* * The owner of record for root is not really important because it * will never be used. @@ -360,32 +358,10 @@ vm_radix_insert(struct vm_radix *rtree, vm_page_t page) panic("%s: key %jx is already present", __func__, (uintmax_t)index); clev = vm_radix_keydiff(m->pindex, index); - - /* - * During node allocation the trie that is being - * walked can be modified because of recursing radix - * trie operations. - * If this is the case, the recursing functions signal - * such situation and the insert operation must - * start from scratch again. - * The freed radix node will then be in the UMA - * caches very likely to avoid the same situation - * to happen. - */ - rtree->rt_flags |= RT_INSERT_INPROG; tmp = vm_radix_node_get(vm_radix_trimkey(index, clev + 1), 2, clev); - rtree->rt_flags &= ~RT_INSERT_INPROG; - if (tmp == NULL) { - rtree->rt_flags &= ~RT_TRIE_MODIFIED; + if (tmp == NULL) return (ENOMEM); - } - if ((rtree->rt_flags & RT_TRIE_MODIFIED) != 0) { - rtree->rt_flags &= ~RT_TRIE_MODIFIED; - tmp->rn_count = 0; - vm_radix_node_put(tmp); - goto restart; - } *parentp = tmp; vm_radix_addpage(tmp, index, clev, page); vm_radix_addpage(tmp, m->pindex, clev, m); @@ -409,21 +385,9 @@ vm_radix_insert(struct vm_radix *rtree, vm_page_t page) */ newind = rnode->rn_owner; clev = vm_radix_keydiff(newind, index); - - /* See the comments above. */ - rtree->rt_flags |= RT_INSERT_INPROG; tmp = vm_radix_node_get(vm_radix_trimkey(index, clev + 1), 2, clev); - rtree->rt_flags &= ~RT_INSERT_INPROG; - if (tmp == NULL) { - rtree->rt_flags &= ~RT_TRIE_MODIFIED; + if (tmp == NULL) return (ENOMEM); - } - if ((rtree->rt_flags & RT_TRIE_MODIFIED) != 0) { - rtree->rt_flags &= ~RT_TRIE_MODIFIED; - tmp->rn_count = 0; - vm_radix_node_put(tmp); - goto restart; - } *parentp = tmp; vm_radix_addpage(tmp, index, clev, page); slot = vm_radix_slot(newind, clev); @@ -708,20 +672,6 @@ vm_radix_remove(struct vm_radix *rtree, vm_pindex_t index) vm_page_t m; int i, slot; - /* - * Detect if a page is going to be removed from a trie which is - * already undergoing another trie operation. - * Right now this is only possible for vm_radix_remove() recursing - * into vm_radix_insert(). - * If this is the case, the caller must be notified about this - * situation. It will also takecare to update the RT_TRIE_MODIFIED - * accordingly. - * The RT_TRIE_MODIFIED bit is set here because the remove operation - * will always succeed. - */ - if ((rtree->rt_flags & RT_INSERT_INPROG) != 0) - rtree->rt_flags |= RT_TRIE_MODIFIED; - rnode = vm_radix_getroot(rtree); if (vm_radix_isleaf(rnode)) { m = vm_radix_topage(rnode); @@ -776,9 +726,6 @@ vm_radix_reclaim_allnodes(struct vm_radix *rtree) { struct vm_radix_node *root; - KASSERT((rtree->rt_flags & RT_INSERT_INPROG) == 0, - ("vm_radix_reclaim_allnodes: unexpected trie recursion")); - root = vm_radix_getroot(rtree); if (root == NULL) return;