Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On Wed, 17 Aug 2016, aruna.ramakris...@oracle.com wrote: > I'll send out an updated slab counters patch with Joonsoo's suggested fix > tomorrow (nr_slabs will be unsigned long for SLAB only, and there will be a > separate definition for SLUB), and once that's in, I'll create a new patch > that makes nr_slabs common for SLAB and SLUB, and also converts total_objects > to unsigned long. Maybe it can include some more cleanup too. Does that sound > acceptable? Thats fine.
Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On 08/16/2016 08:52 AM, Christoph Lameter wrote: On Tue, 16 Aug 2016, Joonsoo Kim wrote: In SLUB, nr_slabs is manipulated without holding a lock so atomic operation should be used. It could be moved under the node lock. Christoph, Joonsoo, I agree that nr_slabs could be common between SLAB and SLUB, but I think that should be a separate patch, since converting nr_slabs to unsigned long for SLUB will cause quite a bit of change in mm/slub.c that is not related to adding counters to SLAB. I'll send out an updated slab counters patch with Joonsoo's suggested fix tomorrow (nr_slabs will be unsigned long for SLAB only, and there will be a separate definition for SLUB), and once that's in, I'll create a new patch that makes nr_slabs common for SLAB and SLUB, and also converts total_objects to unsigned long. Maybe it can include some more cleanup too. Does that sound acceptable? Thanks, Aruna
Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On Tue, 16 Aug 2016, Joonsoo Kim wrote: > In SLUB, nr_slabs is manipulated without holding a lock so atomic > operation should be used. It could be moved under the node lock.
Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On Fri, Aug 05, 2016 at 09:21:56AM -0500, Christoph Lameter wrote: > On Fri, 5 Aug 2016, Joonsoo Kim wrote: > > > If above my comments are fixed, all counting would be done with > > holding a lock. So, atomic definition isn't needed for the SLAB. > > Ditto for slub. struct kmem_cache_node is alrady defined in mm/slab.h. > Thus it is a common definition already and can be used by both. > > Making nr_slabs and total_objects unsigned long would be great. In SLUB, nr_slabs is manipulated without holding a lock so atomic operation should be used. Anyway, Aruna. Could you handle my comment? Thank.
Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On Fri, 5 Aug 2016, Joonsoo Kim wrote: > If above my comments are fixed, all counting would be done with > holding a lock. So, atomic definition isn't needed for the SLAB. Ditto for slub. struct kmem_cache_node is alrady defined in mm/slab.h. Thus it is a common definition already and can be used by both. Making nr_slabs and total_objects unsigned long would be great.
Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On Thu, 4 Aug 2016, Aruna Ramakrishna wrote: > On large systems, when some slab caches grow to millions of objects (and > many gigabytes), running 'cat /proc/slabinfo' can take up to 1-2 seconds. > During this time, interrupts are disabled while walking the slab lists > (slabs_full, slabs_partial, and slabs_free) for each node, and this > sometimes causes timeouts in other drivers (for instance, Infiniband). Acked-by: Christoph Lameter
Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
2016-08-05 4:01 GMT+09:00 Aruna Ramakrishna :
> On large systems, when some slab caches grow to millions of objects (and
> many gigabytes), running 'cat /proc/slabinfo' can take up to 1-2 seconds.
> During this time, interrupts are disabled while walking the slab lists
> (slabs_full, slabs_partial, and slabs_free) for each node, and this
> sometimes causes timeouts in other drivers (for instance, Infiniband).
>
> This patch optimizes 'cat /proc/slabinfo' by maintaining a counter for
> total number of allocated slabs per node, per cache. This counter is
> updated when a slab is created or destroyed. This enables us to skip
> traversing the slabs_full list while gathering slabinfo statistics, and
> since slabs_full tends to be the biggest list when the cache is large, it
> results in a dramatic performance improvement. Getting slabinfo statistics
> now only requires walking the slabs_free and slabs_partial lists, and
> those lists are usually much smaller than slabs_full. We tested this after
> growing the dentry cache to 70GB, and the performance improved from 2s to
> 5ms.
>
> Signed-off-by: Aruna Ramakrishna
> Cc: Mike Kravetz
> Cc: Christoph Lameter
> Cc: Pekka Enberg
> Cc: David Rientjes
> Cc: Joonsoo Kim
> Cc: Andrew Morton
> ---
> Note: this has been tested only on x86_64.
>
> mm/slab.c | 25 -
> mm/slab.h | 15 ++-
> mm/slub.c | 19 +--
> 3 files changed, 31 insertions(+), 28 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 261147b..d683840 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -233,6 +233,7 @@ static void kmem_cache_node_init(struct kmem_cache_node
> *parent)
> spin_lock_init(&parent->list_lock);
> parent->free_objects = 0;
> parent->free_touched = 0;
> + atomic_long_set(&parent->nr_slabs, 0);
> }
>
> #define MAKE_LIST(cachep, listp, slab, nodeid) \
> @@ -2333,6 +2334,7 @@ static int drain_freelist(struct kmem_cache *cache,
> n->free_objects -= cache->num;
> spin_unlock_irq(&n->list_lock);
> slab_destroy(cache, page);
> + atomic_long_dec(&n->nr_slabs);
> nr_freed++;
> }
Please decrease counter when a slab is detached from the list.
Otherwise, there would be inconsistent between counter and
number of attached slab on the list.
> out:
> @@ -2736,6 +2738,8 @@ static struct page *cache_grow_begin(struct kmem_cache
> *cachep,
> if (gfpflags_allow_blocking(local_flags))
> local_irq_disable();
>
> + atomic_long_inc(&n->nr_slabs);
> +
> return page;
Please increase counter when a slab is attached to the list
in cache_grow_end().
> opps1:
> @@ -3455,6 +3459,7 @@ static void free_block(struct kmem_cache *cachep, void
> **objpp,
>
> page = list_last_entry(&n->slabs_free, struct page, lru);
> list_move(&page->lru, list);
> + atomic_long_dec(&n->nr_slabs);
> }
> }
>
> @@ -4111,6 +4116,8 @@ void get_slabinfo(struct kmem_cache *cachep, struct
> slabinfo *sinfo)
> unsigned long num_objs;
> unsigned long active_slabs = 0;
> unsigned long num_slabs, free_objects = 0, shared_avail = 0;
> + unsigned long num_slabs_partial = 0, num_slabs_free = 0;
> + unsigned long num_slabs_full = 0;
> const char *name;
> char *error = NULL;
> int node;
> @@ -4120,36 +4127,36 @@ void get_slabinfo(struct kmem_cache *cachep, struct
> slabinfo *sinfo)
> num_slabs = 0;
> for_each_kmem_cache_node(cachep, node, n) {
>
> + num_slabs += node_nr_slabs(n);
> check_irq_on();
> spin_lock_irq(&n->list_lock);
>
> - list_for_each_entry(page, &n->slabs_full, lru) {
> - if (page->active != cachep->num && !error)
> - error = "slabs_full accounting error";
> - active_objs += cachep->num;
> - active_slabs++;
> - }
> list_for_each_entry(page, &n->slabs_partial, lru) {
> if (page->active == cachep->num && !error)
> error = "slabs_partial accounting error";
> if (!page->active && !error)
> error = "slabs_partial accounting error";
> active_objs += page->active;
> - active_slabs++;
> + num_slabs_partial++;
> }
> +
> list_for_each_entry(page, &n->slabs_free, lru) {
> if (page->active && !error)
> error = "slabs_free accounting error";
> - num_slabs++;
> + num_slabs_free++;
> }
> +
> free_objects += n->free_objects;
> if (n->shared
Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On 08/04/2016 02:06 PM, Andrew Morton wrote: On Thu, 4 Aug 2016 12:01:13 -0700 Aruna Ramakrishna wrote: On large systems, when some slab caches grow to millions of objects (and many gigabytes), running 'cat /proc/slabinfo' can take up to 1-2 seconds. During this time, interrupts are disabled while walking the slab lists (slabs_full, slabs_partial, and slabs_free) for each node, and this sometimes causes timeouts in other drivers (for instance, Infiniband). This patch optimizes 'cat /proc/slabinfo' by maintaining a counter for total number of allocated slabs per node, per cache. This counter is updated when a slab is created or destroyed. This enables us to skip traversing the slabs_full list while gathering slabinfo statistics, and since slabs_full tends to be the biggest list when the cache is large, it results in a dramatic performance improvement. Getting slabinfo statistics now only requires walking the slabs_free and slabs_partial lists, and those lists are usually much smaller than slabs_full. We tested this after growing the dentry cache to 70GB, and the performance improved from 2s to 5ms. I assume this is tested on both slab and slub? It isn't the smallest of patches but given the seriousness of the problem I think I'll tag it for -stable backporting. This was only sanity-checked on slub. The performance tests were only run on slab. Thanks, Aruna
Re: [PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On Thu, 4 Aug 2016 12:01:13 -0700 Aruna Ramakrishna wrote: > On large systems, when some slab caches grow to millions of objects (and > many gigabytes), running 'cat /proc/slabinfo' can take up to 1-2 seconds. > During this time, interrupts are disabled while walking the slab lists > (slabs_full, slabs_partial, and slabs_free) for each node, and this > sometimes causes timeouts in other drivers (for instance, Infiniband). > > This patch optimizes 'cat /proc/slabinfo' by maintaining a counter for > total number of allocated slabs per node, per cache. This counter is > updated when a slab is created or destroyed. This enables us to skip > traversing the slabs_full list while gathering slabinfo statistics, and > since slabs_full tends to be the biggest list when the cache is large, it > results in a dramatic performance improvement. Getting slabinfo statistics > now only requires walking the slabs_free and slabs_partial lists, and > those lists are usually much smaller than slabs_full. We tested this after > growing the dentry cache to 70GB, and the performance improved from 2s to > 5ms. I assume this is tested on both slab and slub? It isn't the smallest of patches but given the seriousness of the problem I think I'll tag it for -stable backporting.
[PATCH v2] mm/slab: Improve performance of gathering slabinfo stats
On large systems, when some slab caches grow to millions of objects (and
many gigabytes), running 'cat /proc/slabinfo' can take up to 1-2 seconds.
During this time, interrupts are disabled while walking the slab lists
(slabs_full, slabs_partial, and slabs_free) for each node, and this
sometimes causes timeouts in other drivers (for instance, Infiniband).
This patch optimizes 'cat /proc/slabinfo' by maintaining a counter for
total number of allocated slabs per node, per cache. This counter is
updated when a slab is created or destroyed. This enables us to skip
traversing the slabs_full list while gathering slabinfo statistics, and
since slabs_full tends to be the biggest list when the cache is large, it
results in a dramatic performance improvement. Getting slabinfo statistics
now only requires walking the slabs_free and slabs_partial lists, and
those lists are usually much smaller than slabs_full. We tested this after
growing the dentry cache to 70GB, and the performance improved from 2s to
5ms.
Signed-off-by: Aruna Ramakrishna
Cc: Mike Kravetz
Cc: Christoph Lameter
Cc: Pekka Enberg
Cc: David Rientjes
Cc: Joonsoo Kim
Cc: Andrew Morton
---
Note: this has been tested only on x86_64.
mm/slab.c | 25 -
mm/slab.h | 15 ++-
mm/slub.c | 19 +--
3 files changed, 31 insertions(+), 28 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index 261147b..d683840 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -233,6 +233,7 @@ static void kmem_cache_node_init(struct kmem_cache_node
*parent)
spin_lock_init(&parent->list_lock);
parent->free_objects = 0;
parent->free_touched = 0;
+ atomic_long_set(&parent->nr_slabs, 0);
}
#define MAKE_LIST(cachep, listp, slab, nodeid) \
@@ -2333,6 +2334,7 @@ static int drain_freelist(struct kmem_cache *cache,
n->free_objects -= cache->num;
spin_unlock_irq(&n->list_lock);
slab_destroy(cache, page);
+ atomic_long_dec(&n->nr_slabs);
nr_freed++;
}
out:
@@ -2736,6 +2738,8 @@ static struct page *cache_grow_begin(struct kmem_cache
*cachep,
if (gfpflags_allow_blocking(local_flags))
local_irq_disable();
+ atomic_long_inc(&n->nr_slabs);
+
return page;
opps1:
@@ -3455,6 +3459,7 @@ static void free_block(struct kmem_cache *cachep, void
**objpp,
page = list_last_entry(&n->slabs_free, struct page, lru);
list_move(&page->lru, list);
+ atomic_long_dec(&n->nr_slabs);
}
}
@@ -4111,6 +4116,8 @@ void get_slabinfo(struct kmem_cache *cachep, struct
slabinfo *sinfo)
unsigned long num_objs;
unsigned long active_slabs = 0;
unsigned long num_slabs, free_objects = 0, shared_avail = 0;
+ unsigned long num_slabs_partial = 0, num_slabs_free = 0;
+ unsigned long num_slabs_full = 0;
const char *name;
char *error = NULL;
int node;
@@ -4120,36 +4127,36 @@ void get_slabinfo(struct kmem_cache *cachep, struct
slabinfo *sinfo)
num_slabs = 0;
for_each_kmem_cache_node(cachep, node, n) {
+ num_slabs += node_nr_slabs(n);
check_irq_on();
spin_lock_irq(&n->list_lock);
- list_for_each_entry(page, &n->slabs_full, lru) {
- if (page->active != cachep->num && !error)
- error = "slabs_full accounting error";
- active_objs += cachep->num;
- active_slabs++;
- }
list_for_each_entry(page, &n->slabs_partial, lru) {
if (page->active == cachep->num && !error)
error = "slabs_partial accounting error";
if (!page->active && !error)
error = "slabs_partial accounting error";
active_objs += page->active;
- active_slabs++;
+ num_slabs_partial++;
}
+
list_for_each_entry(page, &n->slabs_free, lru) {
if (page->active && !error)
error = "slabs_free accounting error";
- num_slabs++;
+ num_slabs_free++;
}
+
free_objects += n->free_objects;
if (n->shared)
shared_avail += n->shared->avail;
spin_unlock_irq(&n->list_lock);
}
- num_slabs += active_slabs;
num_objs = num_slabs * cachep->num;
+ active_slabs = num_slabs - num_slabs_free;
+ num_slabs_full = num_slabs - (num_slabs_partial + num_slabs_free);
+ active_objs += (num_slabs_full * cachep->num);
+
if (num_objs - active_objs != free_objects && !error)
error = "free_objects accounting error";
