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Message-ID: <20140227073258.GA11087@meta-silence.Home>
Date: Thu, 27 Feb 2014 15:32:58 +0800
From: Jianyu Zhan <nasa4836@...il.com>
To: linux-mm@...ck.org
Cc: nasa4836@...il.com, cl@...ux-foundation.org, penberg@...nel.org,
mpm@...enic.com, linux-kernel@...r.kernel.org
Subject: [PATCH] mm/slab.c: cleanup outdated comments and unify variables
naming
As time goes, the code changes a lot, and this leads to that
some old-days comments scatter around , which instead of faciliating
understanding, but make more confusion. So this patch cleans up them.
Also, this patch unifies some variables naming.
Signed-off-by: Jianyu Zhan <nasa4836@...il.com>
---
mm/slab.c | 66 +++++++++++++++++++++++++++++++--------------------------------
1 file changed, 32 insertions(+), 34 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index b264214..5678673 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -277,8 +277,8 @@ static void kmem_cache_node_init(struct kmem_cache_node *parent)
* OTOH the cpuarrays can contain lots of objects,
* which could lock up otherwise freeable slabs.
*/
-#define REAPTIMEOUT_CPUC (2*HZ)
-#define REAPTIMEOUT_LIST3 (4*HZ)
+#define REAPTIMEOUT_AC (2*HZ)
+#define REAPTIMEOUT_NODE (4*HZ)
#if STATS
#define STATS_INC_ACTIVE(x) ((x)->num_active++)
@@ -1067,7 +1067,7 @@ static int init_cache_node_node(int node)
list_for_each_entry(cachep, &slab_caches, list) {
/*
- * Set up the size64 kmemlist for cpu before we can
+ * Set up the kmem_cache_node for cpu before we can
* begin anything. Make sure some other cpu on this
* node has not already allocated this
*/
@@ -1076,12 +1076,12 @@ static int init_cache_node_node(int node)
if (!n)
return -ENOMEM;
kmem_cache_node_init(n);
- n->next_reap = jiffies + REAPTIMEOUT_LIST3 +
- ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
+ n->next_reap = jiffies + REAPTIMEOUT_NODE +
+ ((unsigned long)cachep) % REAPTIMEOUT_NODE;
/*
- * The l3s don't come and go as CPUs come and
- * go. slab_mutex is sufficient
+ * The kmem_cache_nodes don't come and go as CPUs
+ * come and go. slab_mutex is sufficient
* protection here.
*/
cachep->node[node] = n;
@@ -1406,8 +1406,8 @@ static void __init set_up_node(struct kmem_cache *cachep, int index)
for_each_online_node(node) {
cachep->node[node] = &init_kmem_cache_node[index + node];
cachep->node[node]->next_reap = jiffies +
- REAPTIMEOUT_LIST3 +
- ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
+ REAPTIMEOUT_NODE +
+ ((unsigned long)cachep) % REAPTIMEOUT_NODE;
}
}
@@ -2103,8 +2103,8 @@ static int __init_refok setup_cpu_cache(struct kmem_cache *cachep, gfp_t gfp)
}
}
cachep->node[numa_mem_id()]->next_reap =
- jiffies + REAPTIMEOUT_LIST3 +
- ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
+ jiffies + REAPTIMEOUT_NODE +
+ ((unsigned long)cachep) % REAPTIMEOUT_NODE;
cpu_cache_get(cachep)->avail = 0;
cpu_cache_get(cachep)->limit = BOOT_CPUCACHE_ENTRIES;
@@ -2300,10 +2300,10 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
if (flags & CFLGS_OFF_SLAB) {
cachep->freelist_cache = kmalloc_slab(freelist_size, 0u);
/*
- * This is a possibility for one of the malloc_sizes caches.
+ * This is a possibility for one of the kmalloc_{dma,}_caches.
* But since we go off slab only for object size greater than
- * PAGE_SIZE/8, and malloc_sizes gets created in ascending order,
- * this should not happen at all.
+ * PAGE_SIZE/8, and kmalloc_{dma,}_caches get created
+ * in ascending order,this should not happen at all.
* But leave a BUG_ON for some lucky dude.
*/
BUG_ON(ZERO_OR_NULL_PTR(cachep->freelist_cache));
@@ -2511,14 +2511,17 @@ int __kmem_cache_shutdown(struct kmem_cache *cachep)
/*
* Get the memory for a slab management obj.
- * For a slab cache when the slab descriptor is off-slab, slab descriptors
- * always come from malloc_sizes caches. The slab descriptor cannot
- * come from the same cache which is getting created because,
- * when we are searching for an appropriate cache for these
- * descriptors in kmem_cache_create, we search through the malloc_sizes array.
- * If we are creating a malloc_sizes cache here it would not be visible to
- * kmem_find_general_cachep till the initialization is complete.
- * Hence we cannot have freelist_cache same as the original cache.
+ *
+ * For a slab cache when the slab descriptor is off-slab, the
+ * slab descriptor can't come from the same cache which is being created,
+ * Because if it is the case, that means we defer the creation of
+ * the kmalloc_{dma,}_cache of size sizeof(slab descriptor) to this point.
+ * And we eventually call down to __kmem_cache_create(), which
+ * in turn looks up in the kmalloc_{dma,}_caches for the disired-size one.
+ * This is a "chicken-and-egg" problem.
+ *
+ * So the off-slab slab descriptor shall come from the kmalloc_{dma,}_caches,
+ * which are all initialized during kmem_cache_init().
*/
static void *alloc_slabmgmt(struct kmem_cache *cachep,
struct page *page, int colour_off,
@@ -3320,7 +3323,7 @@ slab_alloc(struct kmem_cache *cachep, gfp_t flags, unsigned long caller)
}
/*
- * Caller needs to acquire correct kmem_list's list_lock
+ * Caller needs to acquire correct kmem_cache_node's list_lock
*/
static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects,
int node)
@@ -3574,11 +3577,6 @@ static __always_inline void *__do_kmalloc(size_t size, gfp_t flags,
struct kmem_cache *cachep;
void *ret;
- /* If you want to save a few bytes .text space: replace
- * __ with kmem_.
- * Then kmalloc uses the uninlined functions instead of the inline
- * functions.
- */
cachep = kmalloc_slab(size, flags);
if (unlikely(ZERO_OR_NULL_PTR(cachep)))
return cachep;
@@ -3670,7 +3668,7 @@ EXPORT_SYMBOL(kfree);
/*
* This initializes kmem_cache_node or resizes various caches for all nodes.
*/
-static int alloc_kmemlist(struct kmem_cache *cachep, gfp_t gfp)
+static int alloc_kmem_cache_node(struct kmem_cache *cachep, gfp_t gfp)
{
int node;
struct kmem_cache_node *n;
@@ -3726,8 +3724,8 @@ static int alloc_kmemlist(struct kmem_cache *cachep, gfp_t gfp)
}
kmem_cache_node_init(n);
- n->next_reap = jiffies + REAPTIMEOUT_LIST3 +
- ((unsigned long)cachep) % REAPTIMEOUT_LIST3;
+ n->next_reap = jiffies + REAPTIMEOUT_NODE +
+ ((unsigned long)cachep) % REAPTIMEOUT_NODE;
n->shared = new_shared;
n->alien = new_alien;
n->free_limit = (1 + nr_cpus_node(node)) *
@@ -3813,7 +3811,7 @@ static int __do_tune_cpucache(struct kmem_cache *cachep, int limit,
kfree(ccold);
}
kfree(new);
- return alloc_kmemlist(cachep, gfp);
+ return alloc_kmem_cache_node(cachep, gfp);
}
static int do_tune_cpucache(struct kmem_cache *cachep, int limit,
@@ -3982,7 +3980,7 @@ static void cache_reap(struct work_struct *w)
if (time_after(n->next_reap, jiffies))
goto next;
- n->next_reap = jiffies + REAPTIMEOUT_LIST3;
+ n->next_reap = jiffies + REAPTIMEOUT_NODE;
drain_array(searchp, n, n->shared, 0, node);
@@ -4003,7 +4001,7 @@ next:
next_reap_node();
out:
/* Set up the next iteration */
- schedule_delayed_work(work, round_jiffies_relative(REAPTIMEOUT_CPUC));
+ schedule_delayed_work(work, round_jiffies_relative(REAPTIMEOUT_AC));
}
#ifdef CONFIG_SLABINFO
--
1.8.5.3
--
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