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 <AVRomanov@sberdevices.ru>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 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 <AVRomanov@sberdevices.ru>
> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> ---
>  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 (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 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