On 02/04/2014 08:03 PM, Michal Hocko wrote:
> On Mon 03-02-14 19:54:38, Vladimir Davydov wrote:
>> Memcg-awareness turned kmem_cache_create() into a dirty interweaving of
>> memcg-only and except-for-memcg calls. To clean this up, let's create a
>> separate function handling memcg caches creation. Although this will
>> result in the two functions having several hunks of practically the same
>> code, I guess this is the case when readability fully covers the cost of
>> code duplication.
> I don't know. The code is apparently cleaner because calling a function
> with NULL memcg just to go via several if (memcg) branches is ugly as
> hell. But having a duplicated function like this calls for a problem
> later.
>
> Would it be possible to split kmem_cache_create into memcg independant
> part and do the rest in a single memcg branch?
May be, something like the patch attached?
>
>> Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
>> ---
>> include/linux/memcontrol.h | 14 ++---
>> include/linux/slab.h | 9 ++-
>> mm/memcontrol.c | 16 ++----
>> mm/slab_common.c | 130
>> ++++++++++++++++++++++++++------------------
>> 4 files changed, 90 insertions(+), 79 deletions(-)
>>
>> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
>> index 84e4801fc36c..de79a9617e09 100644
>> --- a/include/linux/memcontrol.h
>> +++ b/include/linux/memcontrol.h
>> @@ -500,8 +500,8 @@ int memcg_cache_id(struct mem_cgroup *memcg);
>>
>> char *memcg_create_cache_name(struct mem_cgroup *memcg,
>> struct kmem_cache *root_cache);
>> -int memcg_alloc_cache_params(struct mem_cgroup *memcg, struct kmem_cache *s,
>> - struct kmem_cache *root_cache);
>> +int memcg_alloc_cache_params(struct kmem_cache *s,
>> + struct mem_cgroup *memcg, struct kmem_cache *root_cache);
> Why is the parameters ordering changed? It really doesn't help
> review the patch.
Oh, this is because seeing something like
memcg_alloc_cache_params(NULL, s, NULL);
hurts my brain :-) I prefer to have NULLs in the end.
> Also what does `s' stand for and can we use a more
> descriptive name, please?
Yes, we can call it `cachep', but it would be too long :-/
`s' is the common name for a kmem_cache throughout mm/sl[au]b.c so I
guess it fits here. However, this function certainly needs a comment - I
guess I'll do it along with swapping the function parameters in a
separate patch.
Thanks.
>From 55f0916c794ad25a8bf45566f6d333bea956e0d4 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavy...@parallels.com>
Date: Mon, 3 Feb 2014 19:18:22 +0400
Subject: [PATCH] memcg, slab: separate memcg vs root cache creation paths
Memcg-awareness turned kmem_cache_create() into a dirty interweaving of
memcg-only and except-for-memcg calls. To clean this up, let's create a
separate function handling memcg caches creation. Although this will
result in the two functions having several hunks of practically the same
code, I guess this is the case when readability fully covers the cost of
code duplication.
Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
---
include/linux/slab.h | 9 ++-
mm/memcontrol.c | 12 +---
mm/slab_common.c | 174 +++++++++++++++++++++++++++-----------------------
3 files changed, 101 insertions(+), 94 deletions(-)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 9260abdd67df..e8c95d0bb879 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -113,11 +113,10 @@ void __init kmem_cache_init(void);
int slab_is_available(void);
struct kmem_cache *kmem_cache_create(const char *, size_t, size_t,
- unsigned long,
- void (*)(void *));
-struct kmem_cache *
-kmem_cache_create_memcg(struct mem_cgroup *, const char *, size_t, size_t,
- unsigned long, void (*)(void *), struct kmem_cache *);
+ unsigned long, void (*)(void *));
+#ifdef CONFIG_MEMCG_KMEM
+int kmem_cache_create_memcg(struct mem_cgroup *, struct kmem_cache *);
+#endif
void kmem_cache_destroy(struct kmem_cache *);
int kmem_cache_shrink(struct kmem_cache *);
void kmem_cache_free(struct kmem_cache *, void *);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 43e08b7bb365..3857033c2718 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3495,15 +3495,9 @@ struct create_work {
static void memcg_create_cache_work_func(struct work_struct *w)
{
struct create_work *cw = container_of(w, struct create_work, work);
- struct mem_cgroup *memcg = cw->memcg;
- struct kmem_cache *s = cw->cachep;
- struct kmem_cache *new;
-
- new = kmem_cache_create_memcg(memcg, s->name, s->object_size, s->align,
- (s->flags & ~SLAB_PANIC), s->ctor, s);
- if (new)
- new->allocflags |= __GFP_KMEMCG;
- css_put(&memcg->css);
+
+ kmem_cache_create_memcg(cw->memcg, cw->cachep);
+ css_put(&cw->memcg->css);
kfree(cw);
}
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 11857abf7057..6bee919ece80 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -29,8 +29,7 @@ DEFINE_MUTEX(slab_mutex);
struct kmem_cache *kmem_cache;
#ifdef CONFIG_DEBUG_VM
-static int kmem_cache_sanity_check(struct mem_cgroup *memcg, const char *name,
- size_t size)
+static int kmem_cache_sanity_check(const char *name, size_t size)
{
struct kmem_cache *s = NULL;
@@ -57,13 +56,7 @@ static int kmem_cache_sanity_check(struct mem_cgroup *memcg, const char *name,
}
#if !defined(CONFIG_SLUB) || !defined(CONFIG_SLUB_DEBUG_ON)
- /*
- * For simplicity, we won't check this in the list of memcg
- * caches. We have control over memcg naming, and if there
- * aren't duplicates in the global list, there won't be any
- * duplicates in the memcg lists as well.
- */
- if (!memcg && !strcmp(s->name, name)) {
+ if (!strcmp(s->name, name)) {
pr_err("%s (%s): Cache name already exists.\n",
__func__, name);
dump_stack();
@@ -77,8 +70,7 @@ static int kmem_cache_sanity_check(struct mem_cgroup *memcg, const char *name,
return 0;
}
#else
-static inline int kmem_cache_sanity_check(struct mem_cgroup *memcg,
- const char *name, size_t size)
+static inline int kmem_cache_sanity_check(const char *name, size_t size)
{
return 0;
}
@@ -139,6 +131,47 @@ unsigned long calculate_alignment(unsigned long flags,
return ALIGN(align, sizeof(void *));
}
+static struct kmem_cache *
+do_kmem_cache_create(char *name, size_t object_size, size_t size, size_t align,
+ unsigned long flags, void (*ctor)(void *),
+ struct mem_cgroup *memcg, struct kmem_cache *cachep)
+{
+ struct kmem_cache *s = NULL;
+ int err = -ENOMEM;
+
+ if (!name)
+ goto out;
+
+ s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);
+ if (!s)
+ goto out;
+
+ s->name = name;
+ s->object_size = object_size;
+ s->size = size;
+ s->align = align;
+ s->ctor = ctor;
+
+ err = memcg_alloc_cache_params(memcg, s, cachep);
+ if (err)
+ goto out;
+
+ err = __kmem_cache_create(s, flags);
+ if (err)
+ goto out;
+
+ s->refcount = 1;
+ list_add(&s->list, &slab_caches);
+ memcg_register_cache(s);
+out:
+ if (err) {
+ memcg_free_cache_params(s);
+ kfree(name);
+ kfree(s);
+ s = ERR_PTR(err);
+ }
+ return s;
+}
/*
* kmem_cache_create - Create a cache.
@@ -164,11 +197,9 @@ unsigned long calculate_alignment(unsigned long flags,
* cacheline. This can be beneficial if you're counting cycles as closely
* as davem.
*/
-
struct kmem_cache *
-kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
- size_t align, unsigned long flags, void (*ctor)(void *),
- struct kmem_cache *parent_cache)
+kmem_cache_create(const char *name, size_t size, size_t align,
+ unsigned long flags, void (*ctor)(void *))
{
struct kmem_cache *s = NULL;
int err;
@@ -176,22 +207,10 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
get_online_cpus();
mutex_lock(&slab_mutex);
- err = kmem_cache_sanity_check(memcg, name, size);
+ err = kmem_cache_sanity_check(name, size);
if (err)
goto out_unlock;
- if (memcg) {
- /*
- * Since per-memcg caches are created asynchronously on first
- * allocation (see memcg_kmem_get_cache()), several threads can
- * try to create the same cache, but only one of them may
- * succeed. Therefore if we get here and see the cache has
- * already been created, we silently return NULL.
- */
- if (cache_from_memcg_idx(parent_cache, memcg_cache_id(memcg)))
- goto out_unlock;
- }
-
/*
* Some allocators will constraint the set of valid flags to a subset
* of all flags. We expect them to define CACHE_CREATE_MASK in this
@@ -200,55 +219,20 @@ kmem_cache_create_memcg(struct mem_cgroup *memcg, const char *name, size_t size,
*/
flags &= CACHE_CREATE_MASK;
- if (!memcg) {
- s = __kmem_cache_alias(name, size, align, flags, ctor);
- if (s)
- goto out_unlock;
- }
-
- err = -ENOMEM;
- s = kmem_cache_zalloc(kmem_cache, GFP_KERNEL);
- if (!s)
+ s = __kmem_cache_alias(name, size, align, flags, ctor);
+ if (s)
goto out_unlock;
- s->object_size = s->size = size;
- s->align = calculate_alignment(flags, align, size);
- s->ctor = ctor;
-
- if (memcg)
- s->name = memcg_create_cache_name(memcg, parent_cache);
- else
- s->name = kstrdup(name, GFP_KERNEL);
- if (!s->name)
- goto out_free_cache;
-
- err = memcg_alloc_cache_params(memcg, s, parent_cache);
- if (err)
- goto out_free_cache;
-
- err = __kmem_cache_create(s, flags);
- if (err)
- goto out_free_cache;
-
- s->refcount = 1;
- list_add(&s->list, &slab_caches);
- memcg_register_cache(s);
+ s = do_kmem_cache_create(kstrdup(name, GFP_KERNEL),
+ size, size, calculate_alignment(flags, align, size),
+ flags, ctor, NULL, NULL);
+ err = IS_ERR(s) ? PTR_ERR(s) : 0;
out_unlock:
mutex_unlock(&slab_mutex);
put_online_cpus();
if (err) {
- /*
- * There is no point in flooding logs with warnings or
- * especially crashing the system if we fail to create a cache
- * for a memcg. In this case we will be accounting the memcg
- * allocation to the root cgroup until we succeed to create its
- * own cache, but it isn't that critical.
- */
- if (!memcg)
- return NULL;
-
if (flags & SLAB_PANIC)
panic("kmem_cache_create: Failed to create slab '%s'. Error %d\n",
name, err);
@@ -260,21 +244,51 @@ out_unlock:
return NULL;
}
return s;
-
-out_free_cache:
- memcg_free_cache_params(s);
- kfree(s->name);
- kmem_cache_free(kmem_cache, s);
- goto out_unlock;
}
+EXPORT_SYMBOL(kmem_cache_create);
-struct kmem_cache *
-kmem_cache_create(const char *name, size_t size, size_t align,
- unsigned long flags, void (*ctor)(void *))
+#ifdef CONFIG_MEMCG_KMEM
+/*
+ * kmem_cache_create_memcg - Create a cache for a memory cgroup.
+ * @memcg: The memory cgroup the new cache is for.
+ * @cachep: The parent of the new cache.
+ *
+ * This function creates a kmem cache that will serve allocation requests going
+ * from @memcg to @cachep. The new cache inherits properties from its parent.
+ *
+ * Returns 0 on success, -errno on failure.
+ */
+int kmem_cache_create_memcg(struct mem_cgroup *memcg, struct kmem_cache *cachep)
{
- return kmem_cache_create_memcg(NULL, name, size, align, flags, ctor, NULL);
+ struct kmem_cache *s;
+ int err;
+
+ get_online_cpus();
+ mutex_lock(&slab_mutex);
+
+ /*
+ * Since per-memcg caches are created asynchronously on first
+ * allocation (see memcg_kmem_get_cache()), several threads can try to
+ * create the same cache, but only one of them may succeed.
+ */
+ err = -EEXIST;
+ if (cache_from_memcg_idx(cachep, memcg_cache_id(memcg)))
+ goto out_unlock;
+
+ s = do_kmem_cache_create(memcg_create_cache_name(memcg, cachep),
+ cachep->object_size, cachep->size, cachep->align,
+ cachep->flags & ~SLAB_PANIC, cachep->ctor,
+ memcg, cachep);
+ err = IS_ERR(s) ? PTR_ERR(s) : 0;
+ if (!err)
+ s->allocflags |= __GFP_KMEMCG;
+
+out_unlock:
+ mutex_unlock(&slab_mutex);
+ put_online_cpus();
+ return err;
}
-EXPORT_SYMBOL(kmem_cache_create);
+#endif /* CONFIG_MEMCG_KMEM */
void kmem_cache_destroy(struct kmem_cache *s)
{
--
1.7.10.4
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