From adab7b68189d14504e9f690ee7eb7e98af68301b Mon Sep 17 00:00:00 2001 From: "Tobin C. Harding" Date: Mon, 13 May 2019 17:16:06 -0700 Subject: slob: use slab_list instead of lru Currently we use the page->lru list for maintaining lists of slabs. We have a list_head in the page structure (slab_list) that can be used for this purpose. Doing so makes the code cleaner since we are not overloading the lru list. The slab_list is part of a union within the page struct (included here stripped down): union { struct { /* Page cache and anonymous pages */ struct list_head lru; ... }; struct { dma_addr_t dma_addr; }; struct { /* slab, slob and slub */ union { struct list_head slab_list; struct { /* Partial pages */ struct page *next; int pages; /* Nr of pages left */ int pobjects; /* Approximate count */ }; }; ... Here we see that slab_list and lru are the same bits. We can verify that this change is safe to do by examining the object file produced from slob.c before and after this patch is applied. Steps taken to verify: 1. checkout current tip of Linus' tree commit a667cb7a94d4 ("Merge branch 'akpm' (patches from Andrew)") 2. configure and build (select SLOB allocator) CONFIG_SLOB=y CONFIG_SLAB_MERGE_DEFAULT=y 3. dissasemble object file `objdump -dr mm/slub.o > before.s 4. apply patch 5. build 6. dissasemble object file `objdump -dr mm/slub.o > after.s 7. diff before.s after.s Use slab_list list_head instead of the lru list_head for maintaining lists of slabs. Link: http://lkml.kernel.org/r/20190402230545.2929-4-tobin@kernel.org Signed-off-by: Tobin C. Harding Reviewed-by: Roman Gushchin Acked-by: Christoph Lameter Acked-by: Vlastimil Babka Cc: David Rientjes Cc: Joonsoo Kim Cc: Matthew Wilcox Cc: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slob.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'mm/slob.c') diff --git a/mm/slob.c b/mm/slob.c index 07356e9feaaa..84aefd9b91ee 100644 --- a/mm/slob.c +++ b/mm/slob.c @@ -112,13 +112,13 @@ static inline int slob_page_free(struct page *sp) static void set_slob_page_free(struct page *sp, struct list_head *list) { - list_add(&sp->lru, list); + list_add(&sp->slab_list, list); __SetPageSlobFree(sp); } static inline void clear_slob_page_free(struct page *sp) { - list_del(&sp->lru); + list_del(&sp->slab_list); __ClearPageSlobFree(sp); } @@ -298,7 +298,7 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node) spin_lock_irqsave(&slob_lock, flags); /* Iterate through each partially free page, try to find room */ - list_for_each_entry(sp, slob_list, lru) { + list_for_each_entry(sp, slob_list, slab_list) { bool page_removed_from_list = false; #ifdef CONFIG_NUMA /* @@ -328,8 +328,8 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node) * search time by starting our next search here. (see * Knuth vol 1, sec 2.5, pg 449) */ - if (!list_is_first(&sp->lru, slob_list)) - list_rotate_to_front(&sp->lru, slob_list); + if (!list_is_first(&sp->slab_list, slob_list)) + list_rotate_to_front(&sp->slab_list, slob_list); } break; } @@ -346,7 +346,7 @@ static void *slob_alloc(size_t size, gfp_t gfp, int align, int node) spin_lock_irqsave(&slob_lock, flags); sp->units = SLOB_UNITS(PAGE_SIZE); sp->freelist = b; - INIT_LIST_HEAD(&sp->lru); + INIT_LIST_HEAD(&sp->slab_list); set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE)); set_slob_page_free(sp, slob_list); b = slob_page_alloc(sp, size, align, &_unused); -- cgit v1.2.3