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Subject[PATCH 02/16] slab: change return type of kmem_getpages() to struct page
Date
It is more understandable that kmem_getpages() return struct page.
And, with this, we can reduce one translation from virt addr to page and
makes better code than before. Below is a change of this patch.

* Before
text data bss dec hex filename
22123 23434 4 45561 b1f9 mm/slab.o

* After
text data bss dec hex filename
22074 23434 4 45512 b1c8 mm/slab.o

And this help following patch to remove struct slab's colouroff.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

diff --git a/mm/slab.c b/mm/slab.c
index d9eae39..180f532 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -205,7 +205,7 @@ typedef unsigned int kmem_bufctl_t;
struct slab_rcu {
struct rcu_head head;
struct kmem_cache *cachep;
- void *addr;
+ struct page *page;
};

/*
@@ -1731,7 +1731,8 @@ slab_out_of_memory(struct kmem_cache *cachep, gfp_t gfpflags, int nodeid)
* did not request dmaable memory, we might get it, but that
* would be relatively rare and ignorable.
*/
-static void *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, int nodeid)
+static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
+ int nodeid)
{
struct page *page;
int nr_pages;
@@ -1784,16 +1785,15 @@ static void *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, int nodeid)
kmemcheck_mark_unallocated_pages(page, nr_pages);
}

- return page_address(page);
+ return page;
}

/*
* Interface to system's page release.
*/
-static void kmem_freepages(struct kmem_cache *cachep, void *addr)
+static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
{
unsigned long i = (1 << cachep->gfporder);
- struct page *page = virt_to_page(addr);
const unsigned long nr_freed = i;

kmemcheck_free_shadow(page, cachep->gfporder);
@@ -1815,7 +1815,7 @@ static void kmem_freepages(struct kmem_cache *cachep, void *addr)
memcg_release_pages(cachep, cachep->gfporder);
if (current->reclaim_state)
current->reclaim_state->reclaimed_slab += nr_freed;
- free_memcg_kmem_pages((unsigned long)addr, cachep->gfporder);
+ __free_memcg_kmem_pages(page, cachep->gfporder);
}

static void kmem_rcu_free(struct rcu_head *head)
@@ -1823,7 +1823,7 @@ static void kmem_rcu_free(struct rcu_head *head)
struct slab_rcu *slab_rcu = (struct slab_rcu *)head;
struct kmem_cache *cachep = slab_rcu->cachep;

- kmem_freepages(cachep, slab_rcu->addr);
+ kmem_freepages(cachep, slab_rcu->page);
if (OFF_SLAB(cachep))
kmem_cache_free(cachep->slabp_cache, slab_rcu);
}
@@ -2042,7 +2042,7 @@ static void slab_destroy_debugcheck(struct kmem_cache *cachep, struct slab *slab
*/
static void slab_destroy(struct kmem_cache *cachep, struct slab *slabp)
{
- void *addr = slabp->s_mem - slabp->colouroff;
+ struct page *page = virt_to_head_page(slabp->s_mem);

slab_destroy_debugcheck(cachep, slabp);
if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU)) {
@@ -2050,10 +2050,10 @@ static void slab_destroy(struct kmem_cache *cachep, struct slab *slabp)

slab_rcu = (struct slab_rcu *)slabp;
slab_rcu->cachep = cachep;
- slab_rcu->addr = addr;
+ slab_rcu->page = page;
call_rcu(&slab_rcu->head, kmem_rcu_free);
} else {
- kmem_freepages(cachep, addr);
+ kmem_freepages(cachep, page);
if (OFF_SLAB(cachep))
kmem_cache_free(cachep->slabp_cache, slabp);
}
@@ -2598,11 +2598,12 @@ int __kmem_cache_shutdown(struct kmem_cache *cachep)
* kmem_find_general_cachep till the initialization is complete.
* Hence we cannot have slabp_cache same as the original cache.
*/
-static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,
- int colour_off, gfp_t local_flags,
- int nodeid)
+static struct slab *alloc_slabmgmt(struct kmem_cache *cachep,
+ struct page *page, int colour_off,
+ gfp_t local_flags, int nodeid)
{
struct slab *slabp;
+ void *addr = page_address(page);

if (OFF_SLAB(cachep)) {
/* Slab management obj is off-slab. */
@@ -2619,12 +2620,12 @@ static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,
if (!slabp)
return NULL;
} else {
- slabp = objp + colour_off;
+ slabp = addr + colour_off;
colour_off += cachep->slab_size;
}
slabp->inuse = 0;
slabp->colouroff = colour_off;
- slabp->s_mem = objp + colour_off;
+ slabp->s_mem = addr + colour_off;
slabp->nodeid = nodeid;
slabp->free = 0;
return slabp;
@@ -2735,12 +2736,9 @@ static void slab_put_obj(struct kmem_cache *cachep, struct slab *slabp,
* virtual address for kfree, ksize, and slab debugging.
*/
static void slab_map_pages(struct kmem_cache *cache, struct slab *slab,
- void *addr)
+ struct page *page)
{
int nr_pages;
- struct page *page;
-
- page = virt_to_page(addr);

nr_pages = 1;
if (likely(!PageCompound(page)))
@@ -2758,7 +2756,7 @@ static void slab_map_pages(struct kmem_cache *cache, struct slab *slab,
* kmem_cache_alloc() when there are no active objs left in a cache.
*/
static int cache_grow(struct kmem_cache *cachep,
- gfp_t flags, int nodeid, void *objp)
+ gfp_t flags, int nodeid, struct page *page)
{
struct slab *slabp;
size_t offset;
@@ -2801,18 +2799,18 @@ static int cache_grow(struct kmem_cache *cachep,
* Get mem for the objs. Attempt to allocate a physical page from
* 'nodeid'.
*/
- if (!objp)
- objp = kmem_getpages(cachep, local_flags, nodeid);
- if (!objp)
+ if (!page)
+ page = kmem_getpages(cachep, local_flags, nodeid);
+ if (!page)
goto failed;

/* Get slab management. */
- slabp = alloc_slabmgmt(cachep, objp, offset,
+ slabp = alloc_slabmgmt(cachep, page, offset,
local_flags & ~GFP_CONSTRAINT_MASK, nodeid);
if (!slabp)
goto opps1;

- slab_map_pages(cachep, slabp, objp);
+ slab_map_pages(cachep, slabp, page);

cache_init_objs(cachep, slabp);

@@ -2828,7 +2826,7 @@ static int cache_grow(struct kmem_cache *cachep,
spin_unlock(&n->list_lock);
return 1;
opps1:
- kmem_freepages(cachep, objp);
+ kmem_freepages(cachep, page);
failed:
if (local_flags & __GFP_WAIT)
local_irq_disable();
@@ -3244,18 +3242,20 @@ retry:
* We may trigger various forms of reclaim on the allowed
* set and go into memory reserves if necessary.
*/
+ struct page *page;
+
if (local_flags & __GFP_WAIT)
local_irq_enable();
kmem_flagcheck(cache, flags);
- obj = kmem_getpages(cache, local_flags, numa_mem_id());
+ page = kmem_getpages(cache, local_flags, numa_mem_id());
if (local_flags & __GFP_WAIT)
local_irq_disable();
- if (obj) {
+ if (page) {
/*
* Insert into the appropriate per node queues
*/
- nid = page_to_nid(virt_to_page(obj));
- if (cache_grow(cache, flags, nid, obj)) {
+ nid = page_to_nid(page);
+ if (cache_grow(cache, flags, nid, page)) {
obj = ____cache_alloc_node(cache,
flags | GFP_THISNODE, nid);
if (!obj)
--
1.7.9.5


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