[PATCH] mm: zram: amend SLAB_RECLAIM_ACCOUNT on zspage_cachep

[PATCH] mm: zram: amend SLAB_RECLAIM_ACCOUNT on zspage_cachep

[Huangzhaoyang]

From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

Zspage_cachep is found be merged with other kmem cache during test, which
is not good for debug things(zs_pool->zspage_cachep present to be another
kmem cache in memory dumpfile). It is also neccessary to do so as shrinker has
been registered for zspage. Amending this flag can help kernel to calculate
SLAB_RECLAIMBLE correctly.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
---
 mm/zsmalloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 19b563b..0b0addd 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -328,7 +328,7 @@ static int create_cache(struct zs_pool *pool)
 		return 1;
 
 	pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
-					0, 0, NULL);
+					0, SLAB_RECLAIM_ACCOUNT, NULL);
 	if (!pool->zspage_cachep) {
 		kmem_cache_destroy(pool->handle_cachep);
 		pool->handle_cachep = NULL;
-- 
1.9.1

Re: [PATCH] mm: zram: amend SLAB_RECLAIM_ACCOUNT on zspage_cachep

[Minchan Kim]

On Tue, Jun 08, 2021 at 03:28:17PM +0800, Huangzhaoyang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> 
> Zspage_cachep is found be merged with other kmem cache during test, which
> is not good for debug things(zs_pool->zspage_cachep present to be another
> kmem cache in memory dumpfile). It is also neccessary to do so as shrinker has

It's not a only problem of zsmalloc because slab want to minimize
fragmentation so try to merge several objects if it's allowed.
So I don't think it's particular problem of zsmalloc.
I guess slub has some option maybe "nomerge" if you want it.

> been registered for zspage. Amending this flag can help kernel to calculate
> SLAB_RECLAIMBLE correctly.
> 
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> ---
>  mm/zsmalloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index 19b563b..0b0addd 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -328,7 +328,7 @@ static int create_cache(struct zs_pool *pool)
>  		return 1;
>  
>  	pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
> -					0, 0, NULL);
> +					0, SLAB_RECLAIM_ACCOUNT, NULL);

How does zspage become SLAB_RECLAIM_ACCOUNT?

I took the flag as "cacheable" object. IOW, when the shrinker
ask to reclaim the object, it should reclaim(e.g., discarding)
those objects for reclaming. However, that's not the case
in zsmalloc.

Re: [PATCH] mm: zram: amend SLAB_RECLAIM_ACCOUNT on zspage_cachep

[Zhaoyang Huang]

On Sat, Jun 19, 2021 at 6:02 AM Minchan Kim <minchan@kernel.org> wrote:
>
> On Tue, Jun 08, 2021 at 03:28:17PM +0800, Huangzhaoyang wrote:
> > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> >
> > Zspage_cachep is found be merged with other kmem cache during test, which
> > is not good for debug things(zs_pool->zspage_cachep present to be another
> > kmem cache in memory dumpfile). It is also neccessary to do so as shrinker has
>
> It's not a only problem of zsmalloc because slab want to minimize
> fragmentation so try to merge several objects if it's allowed.
> So I don't think it's particular problem of zsmalloc.
> I guess slub has some option maybe "nomerge" if you want it.

>
> > been registered for zspage. Amending this flag can help kernel to calculate
> > SLAB_RECLAIMBLE correctly.
> >
> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > ---
> >  mm/zsmalloc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> > index 19b563b..0b0addd 100644
> > --- a/mm/zsmalloc.c
> > +++ b/mm/zsmalloc.c
> > @@ -328,7 +328,7 @@ static int create_cache(struct zs_pool *pool)
> >               return 1;
> >
> >       pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
> > -                                     0, 0, NULL);
> > +                                     0, SLAB_RECLAIM_ACCOUNT, NULL);
>
> How does zspage become SLAB_RECLAIM_ACCOUNT?
>
> I took the flag as "cacheable" object. IOW, when the shrinker
> ask to reclaim the object, it should reclaim(e.g., discarding)
> those objects for reclaming. However, that's not the case
> in zsmalloc.
alloc_slab will take the allocated object into account as
SLAB_RECLAIMABLE when this flag set on the kmem_cache

Re: [PATCH] mm: zram: amend SLAB_RECLAIM_ACCOUNT on zspage_cachep

[Minchan Kim]

On Mon, Jun 21, 2021 at 10:35:26AM +0800, Zhaoyang Huang wrote:
> On Sat, Jun 19, 2021 at 6:02 AM Minchan Kim <minchan@kernel.org> wrote:
> >
> > On Tue, Jun 08, 2021 at 03:28:17PM +0800, Huangzhaoyang wrote:
> > > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > >
> > > Zspage_cachep is found be merged with other kmem cache during test, which
> > > is not good for debug things(zs_pool->zspage_cachep present to be another
> > > kmem cache in memory dumpfile). It is also neccessary to do so as shrinker has
> >
> > It's not a only problem of zsmalloc because slab want to minimize
> > fragmentation so try to merge several objects if it's allowed.
> > So I don't think it's particular problem of zsmalloc.
> > I guess slub has some option maybe "nomerge" if you want it.
> 
> >
> > > been registered for zspage. Amending this flag can help kernel to calculate
> > > SLAB_RECLAIMBLE correctly.
> > >
> > > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > > ---
> > >  mm/zsmalloc.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> > > index 19b563b..0b0addd 100644
> > > --- a/mm/zsmalloc.c
> > > +++ b/mm/zsmalloc.c
> > > @@ -328,7 +328,7 @@ static int create_cache(struct zs_pool *pool)
> > >               return 1;
> > >
> > >       pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
> > > -                                     0, 0, NULL);
> > > +                                     0, SLAB_RECLAIM_ACCOUNT, NULL);
> >
> > How does zspage become SLAB_RECLAIM_ACCOUNT?
> >
> > I took the flag as "cacheable" object. IOW, when the shrinker
> > ask to reclaim the object, it should reclaim(e.g., discarding)
> > those objects for reclaming. However, that's not the case
> > in zsmalloc.
> alloc_slab will take the allocated object into account as
> SLAB_RECLAIMABLE when this flag set on the kmem_cache

My point is zspage_cachep is not an reclimable slab cache.
Please describe why you believe it's reclaimable slab.

Re: [PATCH] mm: zram: amend SLAB_RECLAIM_ACCOUNT on zspage_cachep

[Zhaoyang Huang]

On Wed, Jun 23, 2021 at 7:38 AM Minchan Kim <minchan@kernel.org> wrote:
>
> On Mon, Jun 21, 2021 at 10:35:26AM +0800, Zhaoyang Huang wrote:
> > On Sat, Jun 19, 2021 at 6:02 AM Minchan Kim <minchan@kernel.org> wrote:
> > >
> > > On Tue, Jun 08, 2021 at 03:28:17PM +0800, Huangzhaoyang wrote:
> > > > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > > >
> > > > Zspage_cachep is found be merged with other kmem cache during test, which
> > > > is not good for debug things(zs_pool->zspage_cachep present to be another
> > > > kmem cache in memory dumpfile). It is also neccessary to do so as shrinker has
> > >
> > > It's not a only problem of zsmalloc because slab want to minimize
> > > fragmentation so try to merge several objects if it's allowed.
> > > So I don't think it's particular problem of zsmalloc.
> > > I guess slub has some option maybe "nomerge" if you want it.
> >
> > >
> > > > been registered for zspage. Amending this flag can help kernel to calculate
> > > > SLAB_RECLAIMBLE correctly.
> > > >
> > > > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > > > ---
> > > >  mm/zsmalloc.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> > > > index 19b563b..0b0addd 100644
> > > > --- a/mm/zsmalloc.c
> > > > +++ b/mm/zsmalloc.c
> > > > @@ -328,7 +328,7 @@ static int create_cache(struct zs_pool *pool)
> > > >               return 1;
> > > >
> > > >       pool->zspage_cachep = kmem_cache_create("zspage", sizeof(struct zspage),
> > > > -                                     0, 0, NULL);
> > > > +                                     0, SLAB_RECLAIM_ACCOUNT, NULL);
> > >
> > > How does zspage become SLAB_RECLAIM_ACCOUNT?
> > >
> > > I took the flag as "cacheable" object. IOW, when the shrinker
> > > ask to reclaim the object, it should reclaim(e.g., discarding)
> > > those objects for reclaming. However, that's not the case
> > > in zsmalloc.
> > alloc_slab will take the allocated object into account as
> > SLAB_RECLAIMABLE when this flag set on the kmem_cache
>
> My point is zspage_cachep is not an reclimable slab cache.
> Please describe why you believe it's reclaimable slab.
zspage registered slab shrinker via zs_register_shrinker, in which the
zspage be freed to cache