The patch titled
Subject: mm/slob.c: use slab_list instead of lru
has been added to the -mm tree. Its filename is
slob-use-slab_list-instead-of-lru.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/slob-use-slab_list-instead-of-lru.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/slob-use-slab_list-instead-of-lru.patch
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------------------------------------------------------
From: "Tobin C. Harding" <tobin@xxxxxxxxxx>
Subject: mm/slob.c: 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/20190318000234.22049-4-tobin@xxxxxxxxxx
Signed-off-by: Tobin C. Harding <tobin@xxxxxxxxxx>
Reviewed-by: Roman Gushchin <guro@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slob.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
--- a/mm/slob.c~slob-use-slab_list-instead-of-lru
+++ a/mm/slob.c
@@ -112,13 +112,13 @@ static inline int slob_page_free(struct
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);
}
@@ -282,7 +282,7 @@ static void *slob_alloc(size_t size, gfp
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) {
#ifdef CONFIG_NUMA
/*
* If there's a node specification, search for a partial
@@ -299,22 +299,22 @@ static void *slob_alloc(size_t size, gfp
* Cache previous entry because slob_page_alloc() may
* remove sp from slob_list.
*/
- prev = list_prev_entry(sp, lru);
+ prev = list_prev_entry(sp, slab_list);
/* Attempt to alloc */
b = slob_page_alloc(sp, size, align);
if (!b)
continue;
- next = list_next_entry(prev, lru); /* This may or may not be sp */
+ next = list_next_entry(prev, slab_list); /* This may or may not be sp */
/*
* Improve fragment distribution and reduce our average
* search time by starting our next search here. (see
* Knuth vol 1, sec 2.5, pg 449)
*/
- if (!list_is_first(&next->lru, slob_list))
- list_rotate_to_front(&next->lru, slob_list);
+ if (!list_is_first(&next->slab_list, slob_list))
+ list_rotate_to_front(&next->slab_list, slob_list);
break;
}
@@ -331,7 +331,7 @@ static void *slob_alloc(size_t size, gfp
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);
_
Patches currently in -mm which might be from tobin@xxxxxxxxxx are
list-add-function-list_rotate_to_front.patch
slob-respect-list_head-abstraction-layer.patch
slob-use-slab_list-instead-of-lru.patch
slub-add-comments-to-endif-pre-processor-macros.patch
slub-use-slab_list-instead-of-lru.patch
slab-use-slab_list-instead-of-lru.patch
mm-remove-stale-comment-from-page-struct.patch
