From: Chengming Zhou <zhouchengming@bytedance.com>
The current updated scheme (which this series implemented) is:
- node partial slabs: PG_Workingset && !frozen
- cpu partial slabs: !PG_Workingset && !frozen
- cpu slabs: !PG_Workingset && frozen
- full slabs: !PG_Workingset && !frozen
The most important change is that "frozen" bit is not set for the
cpu partial slabs anymore, __slab_free() will grab node list_lock
then check by !PG_Workingset that it's not on a node partial list.
And the "frozen" bit is still kept for the cpu slabs for performance,
since we don't need to grab node list_lock to check whether the
PG_Workingset is set or not if the "frozen" bit is set in __slab_free().
Update related documentations and comments in the source.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
---
mm/slub.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index c20bdf5dab0f..a307d319e82c 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -76,13 +76,22 @@
*
* Frozen slabs
*
- * If a slab is frozen then it is exempt from list management. It is not
- * on any list except per cpu partial list. The processor that froze the
+ * If a slab is frozen then it is exempt from list management. It is
+ * the cpu slab which is actively allocated from by the processor that
+ * froze it and it is not on any list. The processor that froze the
* slab is the one who can perform list operations on the slab. Other
* processors may put objects onto the freelist but the processor that
* froze the slab is the only one that can retrieve the objects from the
* slab's freelist.
*
+ * CPU partial slabs
+ *
+ * The partially empty slabs cached on the CPU partial list are used
+ * for performance reasons, which speeds up the allocation process.
+ * These slabs are not frozen, but are also exempt from list management,
+ * by clearing the PG_workingset flag when moving out of the node
+ * partial list. Please see __slab_free() for more details.
+ *
* list_lock
*
* The list_lock protects the partial and full list on each node and
@@ -2617,8 +2626,7 @@ static void put_partials_cpu(struct kmem_cache *s,
}
/*
- * Put a slab that was just frozen (in __slab_free|get_partial_node) into a
- * partial slab slot if available.
+ * Put a slab into a partial slab slot if available.
*
* If we did not find a slot then simply move all the partials to the
* per node partial list.
--
2.20.1On Thu, 2 Nov 2023, chengming.zhou@linux.dev wrote: > From: Chengming Zhou <zhouchengming@bytedance.com> > > The current updated scheme (which this series implemented) is: > - node partial slabs: PG_Workingset && !frozen > - cpu partial slabs: !PG_Workingset && !frozen > - cpu slabs: !PG_Workingset && frozen > - full slabs: !PG_Workingset && !frozen The above would be good to include in the comments. Acked-by: Christoph Lameter (Ampere) <cl@linux.com>
On 2023/12/5 05:41, Christoph Lameter (Ampere) wrote: > On Thu, 2 Nov 2023, chengming.zhou@linux.dev wrote: > >> From: Chengming Zhou <zhouchengming@bytedance.com> >> >> The current updated scheme (which this series implemented) is: >> - node partial slabs: PG_Workingset && !frozen >> - cpu partial slabs: !PG_Workingset && !frozen >> - cpu slabs: !PG_Workingset && frozen >> - full slabs: !PG_Workingset && !frozen > > The above would be good to include in the comments. > > Acked-by: Christoph Lameter (Ampere) <cl@linux.com> > Thanks for your review and suggestion! Maybe something like this: diff --git a/mm/slub.c b/mm/slub.c index 623c17a4cdd6..21f88bd9c16b 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -93,6 +93,12 @@ * by clearing the PG_workingset flag when moving out of the node * partial list. Please see __slab_free() for more details. * + * To sum up, the current scheme is: + * - node partial slab: PG_Workingset && !frozen + * - cpu partial slab: !PG_Workingset && !frozen + * - cpu slab: !PG_Workingset && frozen + * - full slab: !PG_Workingset && !frozen + * * list_lock * * The list_lock protects the partial and full list on each node and
On 12/5/23 07:06, Chengming Zhou wrote: > On 2023/12/5 05:41, Christoph Lameter (Ampere) wrote: >> On Thu, 2 Nov 2023, chengming.zhou@linux.dev wrote: >> >>> From: Chengming Zhou <zhouchengming@bytedance.com> >>> >>> The current updated scheme (which this series implemented) is: >>> - node partial slabs: PG_Workingset && !frozen >>> - cpu partial slabs: !PG_Workingset && !frozen >>> - cpu slabs: !PG_Workingset && frozen >>> - full slabs: !PG_Workingset && !frozen >> >> The above would be good to include in the comments. >> >> Acked-by: Christoph Lameter (Ampere) <cl@linux.com> >> > > Thanks for your review and suggestion! > > Maybe something like this: Thanks, added. > diff --git a/mm/slub.c b/mm/slub.c > index 623c17a4cdd6..21f88bd9c16b 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -93,6 +93,12 @@ > * by clearing the PG_workingset flag when moving out of the node > * partial list. Please see __slab_free() for more details. > * > + * To sum up, the current scheme is: > + * - node partial slab: PG_Workingset && !frozen > + * - cpu partial slab: !PG_Workingset && !frozen > + * - cpu slab: !PG_Workingset && frozen > + * - full slab: !PG_Workingset && !frozen > + * > * list_lock > * > * The list_lock protects the partial and full list on each node and
On Thu, Nov 2, 2023 at 12:25 PM <chengming.zhou@linux.dev> wrote: > > From: Chengming Zhou <zhouchengming@bytedance.com> > > The current updated scheme (which this series implemented) is: > - node partial slabs: PG_Workingset && !frozen > - cpu partial slabs: !PG_Workingset && !frozen > - cpu slabs: !PG_Workingset && frozen > - full slabs: !PG_Workingset && !frozen > > The most important change is that "frozen" bit is not set for the > cpu partial slabs anymore, __slab_free() will grab node list_lock > then check by !PG_Workingset that it's not on a node partial list. > > And the "frozen" bit is still kept for the cpu slabs for performance, > since we don't need to grab node list_lock to check whether the > PG_Workingset is set or not if the "frozen" bit is set in __slab_free(). > > Update related documentations and comments in the source. > > Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> > Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> > --- > mm/slub.c | 16 ++++++++++++---- > 1 file changed, 12 insertions(+), 4 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index c20bdf5dab0f..a307d319e82c 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -76,13 +76,22 @@ > * > * Frozen slabs > * > - * If a slab is frozen then it is exempt from list management. It is not > - * on any list except per cpu partial list. The processor that froze the > + * If a slab is frozen then it is exempt from list management. It is > + * the cpu slab which is actively allocated from by the processor that > + * froze it and it is not on any list. The processor that froze the > * slab is the one who can perform list operations on the slab. Other > * processors may put objects onto the freelist but the processor that > * froze the slab is the only one that can retrieve the objects from the > * slab's freelist. > * > + * CPU partial slabs > + * > + * The partially empty slabs cached on the CPU partial list are used > + * for performance reasons, which speeds up the allocation process. > + * These slabs are not frozen, but are also exempt from list management, > + * by clearing the PG_workingset flag when moving out of the node > + * partial list. Please see __slab_free() for more details. > + * > * list_lock > * > * The list_lock protects the partial and full list on each node and > @@ -2617,8 +2626,7 @@ static void put_partials_cpu(struct kmem_cache *s, > } > > /* > - * Put a slab that was just frozen (in __slab_free|get_partial_node) into a > - * partial slab slot if available. > + * Put a slab into a partial slab slot if available. > * > * If we did not find a slot then simply move all the partials to the > * per node partial list. > -- Looks good to me, Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Thanks! > 2.20.1 >
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