Hi,
A tiny series that can reduce the number of
find_alloced_obj() invocations (which perform a linear
scan of sub-page) during compaction. Inspired by Alexey
Romanov's findings.
Sergey Senozhatsky (2):
zsmalloc: do not scan for allocated objects in empty zspage
zsmalloc: move migration destination zspage inuse check
mm/zsmalloc.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
--
2.41.0.162.gfafddb0af9-goog
zspage migration can terminate as soon as it moves the last
allocated object from the source zspage. Add a simple helper
zspage_empty() that tests zspage ->inuse on each migration
iteration.
Suggested-by: Alexey Romanov <[email protected]>
Signed-off-by: Sergey Senozhatsky <[email protected]>
---
mm/zsmalloc.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 3f057970504e..5d60eaedc3b7 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1147,6 +1147,11 @@ static bool zspage_full(struct size_class *class, struct zspage *zspage)
return get_zspage_inuse(zspage) == class->objs_per_zspage;
}
+static bool zspage_empty(struct zspage *zspage)
+{
+ return get_zspage_inuse(zspage) == 0;
+}
+
/**
* zs_lookup_class_index() - Returns index of the zsmalloc &size_class
* that hold objects of the provided size.
@@ -1625,6 +1630,10 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
obj_idx++;
record_obj(handle, free_obj);
obj_free(class->size, used_obj);
+
+ /* Stop if there are no more objects to migrate */
+ if (zspage_empty(get_zspage(s_page)))
+ break;
}
/* Remember last position in this iteration */
--
2.41.0.162.gfafddb0af9-goog
Hello!
On Fri, Jun 23, 2023 at 01:40:01PM +0900, Sergey Senozhatsky wrote:
> zspage migration can terminate as soon as it moves the last
> allocated object from the source zspage. Add a simple helper
> zspage_empty() that tests zspage ->inuse on each migration
> iteration.
>
> Suggested-by: Alexey Romanov <[email protected]>
> Signed-off-by: Sergey Senozhatsky <[email protected]>
> ---
> mm/zsmalloc.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 3f057970504e..5d60eaedc3b7 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -1147,6 +1147,11 @@ static bool zspage_full(struct size_class *class, struct zspage *zspage)
> return get_zspage_inuse(zspage) == class->objs_per_zspage;
> }
>
> +static bool zspage_empty(struct zspage *zspage)
> +{
> + return get_zspage_inuse(zspage) == 0;
> +}
> +
> /**
> * zs_lookup_class_index() - Returns index of the zsmalloc &size_class
> * that hold objects of the provided size.
> @@ -1625,6 +1630,10 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
> obj_idx++;
> record_obj(handle, free_obj);
> obj_free(class->size, used_obj);
> +
> + /* Stop if there are no more objects to migrate */
> + if (zspage_empty(get_zspage(s_page)))
> + break;
> }
>
> /* Remember last position in this iteration */
> --
> 2.41.0.162.gfafddb0af9-goog
>
I think we can add similar check in zs_reclaim_page() function.
There we also scan zspage to find the allocated object.
--
Thank you,
Alexey
On Fri, Jun 23, 2023 at 01:40:00PM +0900, Sergey Senozhatsky wrote:
> Hi,
> A tiny series that can reduce the number of
> find_alloced_obj() invocations (which perform a linear
> scan of sub-page) during compaction. Inspired by Alexey
> Romanov's findings.
>
Both patches looks good to me.
In this chance, can we have little more cleanup after these two patches?
From 3cfd4bb0bf395e271f270ee16cb08964ff785a3a Mon Sep 17 00:00:00 2001
From: Minchan Kim <[email protected]>
Date: Fri, 23 Jun 2023 09:45:33 -0700
Subject: [PATCH] zsmalloc: remove zs_compact_control
__zs_compact always putback src_zspage into class list after
migrate_zspage. Thus, we don't need to keep last position of
src_zspage any more. Let's remove it.
Signed-off-by: Minchan Kim <[email protected]>
---
mm/zsmalloc.c | 37 +++++++++----------------------------
1 file changed, 9 insertions(+), 28 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 4a84f7877669..84beadc088b8 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1590,25 +1590,14 @@ static unsigned long find_alloced_obj(struct size_class *class,
return find_tagged_obj(class, page, obj_idx, OBJ_ALLOCATED_TAG);
}
-struct zs_compact_control {
- /* Source spage for migration which could be a subpage of zspage */
- struct page *s_page;
- /* Destination page for migration which should be a first page
- * of zspage. */
- struct page *d_page;
- /* Starting object index within @s_page which used for live object
- * in the subpage. */
- int obj_idx;
-};
-
-static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
- struct zs_compact_control *cc)
+static void migrate_zspage(struct zs_pool *pool, struct zspage *src_zspage,
+ struct zspage *dst_zspage)
{
unsigned long used_obj, free_obj;
unsigned long handle;
- struct page *s_page = cc->s_page;
- struct page *d_page = cc->d_page;
- int obj_idx = cc->obj_idx;
+ int obj_idx = 0;
+ struct page *s_page = get_first_page(src_zspage);
+ struct size_class *class = pool->size_class[src_zspage->class];
while (1) {
handle = find_alloced_obj(class, s_page, &obj_idx);
@@ -1621,24 +1610,20 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
}
used_obj = handle_to_obj(handle);
- free_obj = obj_malloc(pool, get_zspage(d_page), handle);
+ free_obj = obj_malloc(pool, dst_zspage, handle);
zs_object_copy(class, free_obj, used_obj);
obj_idx++;
record_obj(handle, free_obj);
obj_free(class->size, used_obj);
/* Stop if there is no more space */
- if (zspage_full(class, get_zspage(d_page)))
+ if (zspage_full(class, dst_zspage))
break;
/* Stop if there are no more objects to migrate */
- if (zspage_empty(get_zspage(s_page)))
+ if (zspage_empty(src_zspage))
break;
}
-
- /* Remember last position in this iteration */
- cc->s_page = s_page;
- cc->obj_idx = obj_idx;
}
static struct zspage *isolate_src_zspage(struct size_class *class)
@@ -2013,7 +1998,6 @@ static unsigned long zs_can_compact(struct size_class *class)
static unsigned long __zs_compact(struct zs_pool *pool,
struct size_class *class)
{
- struct zs_compact_control cc;
struct zspage *src_zspage = NULL;
struct zspage *dst_zspage = NULL;
unsigned long pages_freed = 0;
@@ -2031,7 +2015,6 @@ static unsigned long __zs_compact(struct zs_pool *pool,
if (!dst_zspage)
break;
migrate_write_lock(dst_zspage);
- cc.d_page = get_first_page(dst_zspage);
}
src_zspage = isolate_src_zspage(class);
@@ -2040,9 +2023,7 @@ static unsigned long __zs_compact(struct zs_pool *pool,
migrate_write_lock_nested(src_zspage);
- cc.obj_idx = 0;
- cc.s_page = get_first_page(src_zspage);
- migrate_zspage(pool, class, &cc);
+ migrate_zspage(pool, src_zspage, dst_zspage);
fg = putback_zspage(class, src_zspage);
migrate_write_unlock(src_zspage);
--
2.41.0.178.g377b9f9a00-goog
On (23/06/23 10:49), Alexey Romanov wrote:
> > +static bool zspage_empty(struct zspage *zspage)
> > +{
> > + return get_zspage_inuse(zspage) == 0;
> > +}
> > +
> > /**
> > * zs_lookup_class_index() - Returns index of the zsmalloc &size_class
> > * that hold objects of the provided size.
> > @@ -1625,6 +1630,10 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
> > obj_idx++;
> > record_obj(handle, free_obj);
> > obj_free(class->size, used_obj);
> > +
> > + /* Stop if there are no more objects to migrate */
> > + if (zspage_empty(get_zspage(s_page)))
> > + break;
> > }
> >
> > /* Remember last position in this iteration */
> > --
> > 2.41.0.162.gfafddb0af9-goog
> >
>
> I think we can add similar check in zs_reclaim_page() function.
> There we also scan zspage to find the allocated object.
LRU was moved to zswap, so zs_reclaim_page() doesn't exist any longer
(in linux-next).
On (23/06/23 10:03), Minchan Kim wrote:
> On Fri, Jun 23, 2023 at 01:40:00PM +0900, Sergey Senozhatsky wrote:
> > Hi,
> > A tiny series that can reduce the number of
> > find_alloced_obj() invocations (which perform a linear
> > scan of sub-page) during compaction. Inspired by Alexey
> > Romanov's findings.
> >
>
> Both patches looks good to me.
Thanks.
> In this chance, can we have little more cleanup after these two patches?
Looks good. I'll pick it up for v2.
On Sat, Jun 24, 2023 at 11:29:17AM +0900, Sergey Senozhatsky wrote:
> On (23/06/23 10:49), Alexey Romanov wrote:
> > > +static bool zspage_empty(struct zspage *zspage)
> > > +{
> > > + return get_zspage_inuse(zspage) == 0;
> > > +}
> > > +
> > > /**
> > > * zs_lookup_class_index() - Returns index of the zsmalloc &size_class
> > > * that hold objects of the provided size.
> > > @@ -1625,6 +1630,10 @@ static void migrate_zspage(struct zs_pool *pool, struct size_class *class,
> > > obj_idx++;
> > > record_obj(handle, free_obj);
> > > obj_free(class->size, used_obj);
> > > +
> > > + /* Stop if there are no more objects to migrate */
> > > + if (zspage_empty(get_zspage(s_page)))
> > > + break;
> > > }
> > >
> > > /* Remember last position in this iteration */
> > > --
> > > 2.41.0.162.gfafddb0af9-goog
> > >
> >
> > I think we can add similar check in zs_reclaim_page() function.
> > There we also scan zspage to find the allocated object.
>
> LRU was moved to zswap, so zs_reclaim_page() doesn't exist any longer
> (in linux-next).
Yeah, sorry. Just looking in current linux master.
--
Thank you,
Alexey