Re: [PATCH v1 3/5] mm: VM can be aware of zram fullness
On Wed, Sep 24, 2014 at 9:06 PM, Minchan Kim wrote:
> On Wed, Sep 24, 2014 at 10:12:18AM -0400, Dan Streetman wrote:
>> On Sun, Sep 21, 2014 at 8:03 PM, Minchan Kim wrote:
>> > VM uses nr_swap_pages to throttle amount of swap when it reclaims
>> > anonymous pages because the nr_swap_pages means freeable space
>> > of swap disk.
>> >
>> > However, it's a problem for zram because zram can limit memory
>> > usage by knob(ie, mem_limit) so that swap out can fail although
>> > VM can see lots of free space from zram disk but no more free
>> > space in zram by the limit. If it happens, VM should notice it
>> > and stop reclaimaing until zram can obtain more free space but
>> > we don't have a way to communicate between VM and zram.
>> >
>> > This patch adds new hint SWAP_FULL so that zram can say to VM
>> > "I'm full" from now on. Then VM cannot reclaim annoymous page
>> > any more. If VM notice swap is full, it can remove swap_info_struct
>> > from swap_avail_head and substract remained freeable space from
>> > nr_swap_pages so that VM can think swap is full until VM frees a
>> > swap and increase nr_swap_pages again.
>> >
>> > Signed-off-by: Minchan Kim
>> > ---
>> > include/linux/blkdev.h | 1 +
>> > mm/swapfile.c | 44 ++--
>> > 2 files changed, 39 insertions(+), 6 deletions(-)
>> >
>> > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> > index c7220409456c..39f074e0acd7 100644
>> > --- a/include/linux/blkdev.h
>> > +++ b/include/linux/blkdev.h
>> > @@ -1611,6 +1611,7 @@ static inline bool
>> > blk_integrity_is_initialized(struct gendisk *g)
>> >
>> > enum swap_blk_hint {
>> > SWAP_FREE,
>> > + SWAP_FULL,
>> > };
>> >
>> > struct block_device_operations {
>> > diff --git a/mm/swapfile.c b/mm/swapfile.c
>> > index 209112cf8b83..71e3df0431b6 100644
>> > --- a/mm/swapfile.c
>> > +++ b/mm/swapfile.c
>> > @@ -493,6 +493,29 @@ static unsigned long scan_swap_map(struct
>> > swap_info_struct *si,
>> > int latency_ration = LATENCY_LIMIT;
>> >
>> > /*
>> > +* If zram is full, we don't need to scan and want to stop swap.
>> > +* For it, we removes si from swap_avail_head and decreases
>> > +* nr_swap_pages to prevent further anonymous reclaim so that
>> > +* VM can restart swap out if zram has a free space.
>> > +* Look at swap_entry_free.
>> > +*/
>> > + if (si->flags & SWP_BLKDEV) {
>> > + struct gendisk *disk = si->bdev->bd_disk;
>> > +
>> > + if (disk->fops->swap_hint && disk->fops->swap_hint(
>> > + si->bdev, SWAP_FULL, NULL)) {
>> > + spin_lock(_avail_lock);
>> > + WARN_ON(plist_node_empty(>avail_list));
>> > + plist_del(>avail_list, _avail_head);
>> > + spin_unlock(_avail_lock);
>> > + atomic_long_sub(si->pages - si->inuse_pages,
>> > + _swap_pages);
>> > + si->full = true;
>> > + return 0;
>> > + }
>> > + }
>> > +
>> > + /*
>> > * We try to cluster swap pages by allocating them sequentially
>> > * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
>> > * way, however, we resort to first-free allocation, starting
>> > @@ -798,6 +821,14 @@ static unsigned char swap_entry_free(struct
>> > swap_info_struct *p,
>> > /* free if no reference */
>> > if (!usage) {
>> > bool was_full;
>> > + struct gendisk *virt_swap = NULL;
>> > +
>> > + /* Check virtual swap */
>> > + if (p->flags & SWP_BLKDEV) {
>> > + virt_swap = p->bdev->bd_disk;
>> > + if (!virt_swap->fops->swap_hint)
>>
>> not a big deal, but can't you just combine these two if's to simplify this?
>
> Do you want this?
>
> if (p->flags & SWP_BLKDEV && p->bdev->bd_disk->fops->swap_hint)
> virt_swap = p->bdev->bd_disk;
ah sorry, i wasn't paying attention there, you're right accessing
virt_swap after you set it is probably better.
>
>
>
>>
>> > + virt_swap = NULL;
>> > + }
>> >
>> > dec_cluster_info_page(p, p->cluster_info, offset);
>> > if (offset < p->lowest_bit)
>> > @@ -814,17 +845,18 @@ static unsigned char swap_entry_free(struct
>> > swap_info_struct *p,
>> > _avail_head);
>> > spin_unlock(_avail_lock);
>> > p->full = false;
>> > + if (virt_swap)
>> > + atomic_long_add(p->pages -
>> > + p->inuse_pages,
>> > + _swap_pages);
>>
>> a comment here might be good,
Re: [PATCH v1 3/5] mm: VM can be aware of zram fullness
On Wed, Sep 24, 2014 at 10:12:18AM -0400, Dan Streetman wrote:
> On Sun, Sep 21, 2014 at 8:03 PM, Minchan Kim wrote:
> > VM uses nr_swap_pages to throttle amount of swap when it reclaims
> > anonymous pages because the nr_swap_pages means freeable space
> > of swap disk.
> >
> > However, it's a problem for zram because zram can limit memory
> > usage by knob(ie, mem_limit) so that swap out can fail although
> > VM can see lots of free space from zram disk but no more free
> > space in zram by the limit. If it happens, VM should notice it
> > and stop reclaimaing until zram can obtain more free space but
> > we don't have a way to communicate between VM and zram.
> >
> > This patch adds new hint SWAP_FULL so that zram can say to VM
> > "I'm full" from now on. Then VM cannot reclaim annoymous page
> > any more. If VM notice swap is full, it can remove swap_info_struct
> > from swap_avail_head and substract remained freeable space from
> > nr_swap_pages so that VM can think swap is full until VM frees a
> > swap and increase nr_swap_pages again.
> >
> > Signed-off-by: Minchan Kim
> > ---
> > include/linux/blkdev.h | 1 +
> > mm/swapfile.c | 44 ++--
> > 2 files changed, 39 insertions(+), 6 deletions(-)
> >
> > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> > index c7220409456c..39f074e0acd7 100644
> > --- a/include/linux/blkdev.h
> > +++ b/include/linux/blkdev.h
> > @@ -1611,6 +1611,7 @@ static inline bool
> > blk_integrity_is_initialized(struct gendisk *g)
> >
> > enum swap_blk_hint {
> > SWAP_FREE,
> > + SWAP_FULL,
> > };
> >
> > struct block_device_operations {
> > diff --git a/mm/swapfile.c b/mm/swapfile.c
> > index 209112cf8b83..71e3df0431b6 100644
> > --- a/mm/swapfile.c
> > +++ b/mm/swapfile.c
> > @@ -493,6 +493,29 @@ static unsigned long scan_swap_map(struct
> > swap_info_struct *si,
> > int latency_ration = LATENCY_LIMIT;
> >
> > /*
> > +* If zram is full, we don't need to scan and want to stop swap.
> > +* For it, we removes si from swap_avail_head and decreases
> > +* nr_swap_pages to prevent further anonymous reclaim so that
> > +* VM can restart swap out if zram has a free space.
> > +* Look at swap_entry_free.
> > +*/
> > + if (si->flags & SWP_BLKDEV) {
> > + struct gendisk *disk = si->bdev->bd_disk;
> > +
> > + if (disk->fops->swap_hint && disk->fops->swap_hint(
> > + si->bdev, SWAP_FULL, NULL)) {
> > + spin_lock(_avail_lock);
> > + WARN_ON(plist_node_empty(>avail_list));
> > + plist_del(>avail_list, _avail_head);
> > + spin_unlock(_avail_lock);
> > + atomic_long_sub(si->pages - si->inuse_pages,
> > + _swap_pages);
> > + si->full = true;
> > + return 0;
> > + }
> > + }
> > +
> > + /*
> > * We try to cluster swap pages by allocating them sequentially
> > * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
> > * way, however, we resort to first-free allocation, starting
> > @@ -798,6 +821,14 @@ static unsigned char swap_entry_free(struct
> > swap_info_struct *p,
> > /* free if no reference */
> > if (!usage) {
> > bool was_full;
> > + struct gendisk *virt_swap = NULL;
> > +
> > + /* Check virtual swap */
> > + if (p->flags & SWP_BLKDEV) {
> > + virt_swap = p->bdev->bd_disk;
> > + if (!virt_swap->fops->swap_hint)
>
> not a big deal, but can't you just combine these two if's to simplify this?
Do you want this?
if (p->flags & SWP_BLKDEV && p->bdev->bd_disk->fops->swap_hint)
virt_swap = p->bdev->bd_disk;
>
> > + virt_swap = NULL;
> > + }
> >
> > dec_cluster_info_page(p, p->cluster_info, offset);
> > if (offset < p->lowest_bit)
> > @@ -814,17 +845,18 @@ static unsigned char swap_entry_free(struct
> > swap_info_struct *p,
> > _avail_head);
> > spin_unlock(_avail_lock);
> > p->full = false;
> > + if (virt_swap)
> > + atomic_long_add(p->pages -
> > + p->inuse_pages,
> > + _swap_pages);
>
> a comment here might be good, to clarify it relies on the check at the
> top of scan_swap_map previously subtracting the same number of pages.
Okay.
>
>
> > }
> >
> > atomic_long_inc(_swap_pages);
> > p->inuse_pages--;
> >
Re: [PATCH v1 3/5] mm: VM can be aware of zram fullness
On Sun, Sep 21, 2014 at 8:03 PM, Minchan Kim wrote:
> VM uses nr_swap_pages to throttle amount of swap when it reclaims
> anonymous pages because the nr_swap_pages means freeable space
> of swap disk.
>
> However, it's a problem for zram because zram can limit memory
> usage by knob(ie, mem_limit) so that swap out can fail although
> VM can see lots of free space from zram disk but no more free
> space in zram by the limit. If it happens, VM should notice it
> and stop reclaimaing until zram can obtain more free space but
> we don't have a way to communicate between VM and zram.
>
> This patch adds new hint SWAP_FULL so that zram can say to VM
> "I'm full" from now on. Then VM cannot reclaim annoymous page
> any more. If VM notice swap is full, it can remove swap_info_struct
> from swap_avail_head and substract remained freeable space from
> nr_swap_pages so that VM can think swap is full until VM frees a
> swap and increase nr_swap_pages again.
>
> Signed-off-by: Minchan Kim
> ---
> include/linux/blkdev.h | 1 +
> mm/swapfile.c | 44 ++--
> 2 files changed, 39 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index c7220409456c..39f074e0acd7 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1611,6 +1611,7 @@ static inline bool blk_integrity_is_initialized(struct
> gendisk *g)
>
> enum swap_blk_hint {
> SWAP_FREE,
> + SWAP_FULL,
> };
>
> struct block_device_operations {
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 209112cf8b83..71e3df0431b6 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -493,6 +493,29 @@ static unsigned long scan_swap_map(struct
> swap_info_struct *si,
> int latency_ration = LATENCY_LIMIT;
>
> /*
> +* If zram is full, we don't need to scan and want to stop swap.
> +* For it, we removes si from swap_avail_head and decreases
> +* nr_swap_pages to prevent further anonymous reclaim so that
> +* VM can restart swap out if zram has a free space.
> +* Look at swap_entry_free.
> +*/
> + if (si->flags & SWP_BLKDEV) {
> + struct gendisk *disk = si->bdev->bd_disk;
> +
> + if (disk->fops->swap_hint && disk->fops->swap_hint(
> + si->bdev, SWAP_FULL, NULL)) {
> + spin_lock(_avail_lock);
> + WARN_ON(plist_node_empty(>avail_list));
> + plist_del(>avail_list, _avail_head);
> + spin_unlock(_avail_lock);
> + atomic_long_sub(si->pages - si->inuse_pages,
> + _swap_pages);
> + si->full = true;
> + return 0;
> + }
> + }
> +
> + /*
> * We try to cluster swap pages by allocating them sequentially
> * in swap. Once we've allocated SWAPFILE_CLUSTER pages this
> * way, however, we resort to first-free allocation, starting
> @@ -798,6 +821,14 @@ static unsigned char swap_entry_free(struct
> swap_info_struct *p,
> /* free if no reference */
> if (!usage) {
> bool was_full;
> + struct gendisk *virt_swap = NULL;
> +
> + /* Check virtual swap */
> + if (p->flags & SWP_BLKDEV) {
> + virt_swap = p->bdev->bd_disk;
> + if (!virt_swap->fops->swap_hint)
not a big deal, but can't you just combine these two if's to simplify this?
> + virt_swap = NULL;
> + }
>
> dec_cluster_info_page(p, p->cluster_info, offset);
> if (offset < p->lowest_bit)
> @@ -814,17 +845,18 @@ static unsigned char swap_entry_free(struct
> swap_info_struct *p,
> _avail_head);
> spin_unlock(_avail_lock);
> p->full = false;
> + if (virt_swap)
> + atomic_long_add(p->pages -
> + p->inuse_pages,
> + _swap_pages);
a comment here might be good, to clarify it relies on the check at the
top of scan_swap_map previously subtracting the same number of pages.
> }
>
> atomic_long_inc(_swap_pages);
> p->inuse_pages--;
> frontswap_invalidate_page(p->type, offset);
> - if (p->flags & SWP_BLKDEV) {
> - struct gendisk *disk = p->bdev->bd_disk;
> - if (disk->fops->swap_hint)
> - disk->fops->swap_hint(p->bdev,
> - SWAP_FREE, (void *)offset);
> - }
> + if (virt_swap)
> +
Re: [PATCH v1 3/5] mm: VM can be aware of zram fullness
On Sun, Sep 21, 2014 at 8:03 PM, Minchan Kim minc...@kernel.org wrote:
VM uses nr_swap_pages to throttle amount of swap when it reclaims
anonymous pages because the nr_swap_pages means freeable space
of swap disk.
However, it's a problem for zram because zram can limit memory
usage by knob(ie, mem_limit) so that swap out can fail although
VM can see lots of free space from zram disk but no more free
space in zram by the limit. If it happens, VM should notice it
and stop reclaimaing until zram can obtain more free space but
we don't have a way to communicate between VM and zram.
This patch adds new hint SWAP_FULL so that zram can say to VM
I'm full from now on. Then VM cannot reclaim annoymous page
any more. If VM notice swap is full, it can remove swap_info_struct
from swap_avail_head and substract remained freeable space from
nr_swap_pages so that VM can think swap is full until VM frees a
swap and increase nr_swap_pages again.
Signed-off-by: Minchan Kim minc...@kernel.org
---
include/linux/blkdev.h | 1 +
mm/swapfile.c | 44 ++--
2 files changed, 39 insertions(+), 6 deletions(-)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c7220409456c..39f074e0acd7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1611,6 +1611,7 @@ static inline bool blk_integrity_is_initialized(struct
gendisk *g)
enum swap_blk_hint {
SWAP_FREE,
+ SWAP_FULL,
};
struct block_device_operations {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 209112cf8b83..71e3df0431b6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -493,6 +493,29 @@ static unsigned long scan_swap_map(struct
swap_info_struct *si,
int latency_ration = LATENCY_LIMIT;
/*
+* If zram is full, we don't need to scan and want to stop swap.
+* For it, we removes si from swap_avail_head and decreases
+* nr_swap_pages to prevent further anonymous reclaim so that
+* VM can restart swap out if zram has a free space.
+* Look at swap_entry_free.
+*/
+ if (si-flags SWP_BLKDEV) {
+ struct gendisk *disk = si-bdev-bd_disk;
+
+ if (disk-fops-swap_hint disk-fops-swap_hint(
+ si-bdev, SWAP_FULL, NULL)) {
+ spin_lock(swap_avail_lock);
+ WARN_ON(plist_node_empty(si-avail_list));
+ plist_del(si-avail_list, swap_avail_head);
+ spin_unlock(swap_avail_lock);
+ atomic_long_sub(si-pages - si-inuse_pages,
+ nr_swap_pages);
+ si-full = true;
+ return 0;
+ }
+ }
+
+ /*
* We try to cluster swap pages by allocating them sequentially
* in swap. Once we've allocated SWAPFILE_CLUSTER pages this
* way, however, we resort to first-free allocation, starting
@@ -798,6 +821,14 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
/* free if no reference */
if (!usage) {
bool was_full;
+ struct gendisk *virt_swap = NULL;
+
+ /* Check virtual swap */
+ if (p-flags SWP_BLKDEV) {
+ virt_swap = p-bdev-bd_disk;
+ if (!virt_swap-fops-swap_hint)
not a big deal, but can't you just combine these two if's to simplify this?
+ virt_swap = NULL;
+ }
dec_cluster_info_page(p, p-cluster_info, offset);
if (offset p-lowest_bit)
@@ -814,17 +845,18 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
swap_avail_head);
spin_unlock(swap_avail_lock);
p-full = false;
+ if (virt_swap)
+ atomic_long_add(p-pages -
+ p-inuse_pages,
+ nr_swap_pages);
a comment here might be good, to clarify it relies on the check at the
top of scan_swap_map previously subtracting the same number of pages.
}
atomic_long_inc(nr_swap_pages);
p-inuse_pages--;
frontswap_invalidate_page(p-type, offset);
- if (p-flags SWP_BLKDEV) {
- struct gendisk *disk = p-bdev-bd_disk;
- if (disk-fops-swap_hint)
- disk-fops-swap_hint(p-bdev,
- SWAP_FREE, (void *)offset);
- }
+ if (virt_swap)
+ virt_swap-fops-swap_hint(p-bdev,
+ SWAP_FREE, (void
Re: [PATCH v1 3/5] mm: VM can be aware of zram fullness
On Wed, Sep 24, 2014 at 10:12:18AM -0400, Dan Streetman wrote:
On Sun, Sep 21, 2014 at 8:03 PM, Minchan Kim minc...@kernel.org wrote:
VM uses nr_swap_pages to throttle amount of swap when it reclaims
anonymous pages because the nr_swap_pages means freeable space
of swap disk.
However, it's a problem for zram because zram can limit memory
usage by knob(ie, mem_limit) so that swap out can fail although
VM can see lots of free space from zram disk but no more free
space in zram by the limit. If it happens, VM should notice it
and stop reclaimaing until zram can obtain more free space but
we don't have a way to communicate between VM and zram.
This patch adds new hint SWAP_FULL so that zram can say to VM
I'm full from now on. Then VM cannot reclaim annoymous page
any more. If VM notice swap is full, it can remove swap_info_struct
from swap_avail_head and substract remained freeable space from
nr_swap_pages so that VM can think swap is full until VM frees a
swap and increase nr_swap_pages again.
Signed-off-by: Minchan Kim minc...@kernel.org
---
include/linux/blkdev.h | 1 +
mm/swapfile.c | 44 ++--
2 files changed, 39 insertions(+), 6 deletions(-)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c7220409456c..39f074e0acd7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1611,6 +1611,7 @@ static inline bool
blk_integrity_is_initialized(struct gendisk *g)
enum swap_blk_hint {
SWAP_FREE,
+ SWAP_FULL,
};
struct block_device_operations {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 209112cf8b83..71e3df0431b6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -493,6 +493,29 @@ static unsigned long scan_swap_map(struct
swap_info_struct *si,
int latency_ration = LATENCY_LIMIT;
/*
+* If zram is full, we don't need to scan and want to stop swap.
+* For it, we removes si from swap_avail_head and decreases
+* nr_swap_pages to prevent further anonymous reclaim so that
+* VM can restart swap out if zram has a free space.
+* Look at swap_entry_free.
+*/
+ if (si-flags SWP_BLKDEV) {
+ struct gendisk *disk = si-bdev-bd_disk;
+
+ if (disk-fops-swap_hint disk-fops-swap_hint(
+ si-bdev, SWAP_FULL, NULL)) {
+ spin_lock(swap_avail_lock);
+ WARN_ON(plist_node_empty(si-avail_list));
+ plist_del(si-avail_list, swap_avail_head);
+ spin_unlock(swap_avail_lock);
+ atomic_long_sub(si-pages - si-inuse_pages,
+ nr_swap_pages);
+ si-full = true;
+ return 0;
+ }
+ }
+
+ /*
* We try to cluster swap pages by allocating them sequentially
* in swap. Once we've allocated SWAPFILE_CLUSTER pages this
* way, however, we resort to first-free allocation, starting
@@ -798,6 +821,14 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
/* free if no reference */
if (!usage) {
bool was_full;
+ struct gendisk *virt_swap = NULL;
+
+ /* Check virtual swap */
+ if (p-flags SWP_BLKDEV) {
+ virt_swap = p-bdev-bd_disk;
+ if (!virt_swap-fops-swap_hint)
not a big deal, but can't you just combine these two if's to simplify this?
Do you want this?
if (p-flags SWP_BLKDEV p-bdev-bd_disk-fops-swap_hint)
virt_swap = p-bdev-bd_disk;
+ virt_swap = NULL;
+ }
dec_cluster_info_page(p, p-cluster_info, offset);
if (offset p-lowest_bit)
@@ -814,17 +845,18 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
swap_avail_head);
spin_unlock(swap_avail_lock);
p-full = false;
+ if (virt_swap)
+ atomic_long_add(p-pages -
+ p-inuse_pages,
+ nr_swap_pages);
a comment here might be good, to clarify it relies on the check at the
top of scan_swap_map previously subtracting the same number of pages.
Okay.
}
atomic_long_inc(nr_swap_pages);
p-inuse_pages--;
frontswap_invalidate_page(p-type, offset);
- if (p-flags SWP_BLKDEV) {
- struct gendisk *disk = p-bdev-bd_disk;
- if (disk-fops-swap_hint)
-
Re: [PATCH v1 3/5] mm: VM can be aware of zram fullness
On Wed, Sep 24, 2014 at 9:06 PM, Minchan Kim minc...@kernel.org wrote:
On Wed, Sep 24, 2014 at 10:12:18AM -0400, Dan Streetman wrote:
On Sun, Sep 21, 2014 at 8:03 PM, Minchan Kim minc...@kernel.org wrote:
VM uses nr_swap_pages to throttle amount of swap when it reclaims
anonymous pages because the nr_swap_pages means freeable space
of swap disk.
However, it's a problem for zram because zram can limit memory
usage by knob(ie, mem_limit) so that swap out can fail although
VM can see lots of free space from zram disk but no more free
space in zram by the limit. If it happens, VM should notice it
and stop reclaimaing until zram can obtain more free space but
we don't have a way to communicate between VM and zram.
This patch adds new hint SWAP_FULL so that zram can say to VM
I'm full from now on. Then VM cannot reclaim annoymous page
any more. If VM notice swap is full, it can remove swap_info_struct
from swap_avail_head and substract remained freeable space from
nr_swap_pages so that VM can think swap is full until VM frees a
swap and increase nr_swap_pages again.
Signed-off-by: Minchan Kim minc...@kernel.org
---
include/linux/blkdev.h | 1 +
mm/swapfile.c | 44 ++--
2 files changed, 39 insertions(+), 6 deletions(-)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c7220409456c..39f074e0acd7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1611,6 +1611,7 @@ static inline bool
blk_integrity_is_initialized(struct gendisk *g)
enum swap_blk_hint {
SWAP_FREE,
+ SWAP_FULL,
};
struct block_device_operations {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 209112cf8b83..71e3df0431b6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -493,6 +493,29 @@ static unsigned long scan_swap_map(struct
swap_info_struct *si,
int latency_ration = LATENCY_LIMIT;
/*
+* If zram is full, we don't need to scan and want to stop swap.
+* For it, we removes si from swap_avail_head and decreases
+* nr_swap_pages to prevent further anonymous reclaim so that
+* VM can restart swap out if zram has a free space.
+* Look at swap_entry_free.
+*/
+ if (si-flags SWP_BLKDEV) {
+ struct gendisk *disk = si-bdev-bd_disk;
+
+ if (disk-fops-swap_hint disk-fops-swap_hint(
+ si-bdev, SWAP_FULL, NULL)) {
+ spin_lock(swap_avail_lock);
+ WARN_ON(plist_node_empty(si-avail_list));
+ plist_del(si-avail_list, swap_avail_head);
+ spin_unlock(swap_avail_lock);
+ atomic_long_sub(si-pages - si-inuse_pages,
+ nr_swap_pages);
+ si-full = true;
+ return 0;
+ }
+ }
+
+ /*
* We try to cluster swap pages by allocating them sequentially
* in swap. Once we've allocated SWAPFILE_CLUSTER pages this
* way, however, we resort to first-free allocation, starting
@@ -798,6 +821,14 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
/* free if no reference */
if (!usage) {
bool was_full;
+ struct gendisk *virt_swap = NULL;
+
+ /* Check virtual swap */
+ if (p-flags SWP_BLKDEV) {
+ virt_swap = p-bdev-bd_disk;
+ if (!virt_swap-fops-swap_hint)
not a big deal, but can't you just combine these two if's to simplify this?
Do you want this?
if (p-flags SWP_BLKDEV p-bdev-bd_disk-fops-swap_hint)
virt_swap = p-bdev-bd_disk;
ah sorry, i wasn't paying attention there, you're right accessing
virt_swap after you set it is probably better.
+ virt_swap = NULL;
+ }
dec_cluster_info_page(p, p-cluster_info, offset);
if (offset p-lowest_bit)
@@ -814,17 +845,18 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
swap_avail_head);
spin_unlock(swap_avail_lock);
p-full = false;
+ if (virt_swap)
+ atomic_long_add(p-pages -
+ p-inuse_pages,
+ nr_swap_pages);
a comment here might be good, to clarify it relies on the check at the
top of scan_swap_map previously subtracting the same number of pages.
Okay.
}
atomic_long_inc(nr_swap_pages);
p-inuse_pages--;
[PATCH v1 3/5] mm: VM can be aware of zram fullness
VM uses nr_swap_pages to throttle amount of swap when it reclaims
anonymous pages because the nr_swap_pages means freeable space
of swap disk.
However, it's a problem for zram because zram can limit memory
usage by knob(ie, mem_limit) so that swap out can fail although
VM can see lots of free space from zram disk but no more free
space in zram by the limit. If it happens, VM should notice it
and stop reclaimaing until zram can obtain more free space but
we don't have a way to communicate between VM and zram.
This patch adds new hint SWAP_FULL so that zram can say to VM
"I'm full" from now on. Then VM cannot reclaim annoymous page
any more. If VM notice swap is full, it can remove swap_info_struct
from swap_avail_head and substract remained freeable space from
nr_swap_pages so that VM can think swap is full until VM frees a
swap and increase nr_swap_pages again.
Signed-off-by: Minchan Kim
---
include/linux/blkdev.h | 1 +
mm/swapfile.c | 44 ++--
2 files changed, 39 insertions(+), 6 deletions(-)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c7220409456c..39f074e0acd7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1611,6 +1611,7 @@ static inline bool blk_integrity_is_initialized(struct
gendisk *g)
enum swap_blk_hint {
SWAP_FREE,
+ SWAP_FULL,
};
struct block_device_operations {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 209112cf8b83..71e3df0431b6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -493,6 +493,29 @@ static unsigned long scan_swap_map(struct swap_info_struct
*si,
int latency_ration = LATENCY_LIMIT;
/*
+* If zram is full, we don't need to scan and want to stop swap.
+* For it, we removes si from swap_avail_head and decreases
+* nr_swap_pages to prevent further anonymous reclaim so that
+* VM can restart swap out if zram has a free space.
+* Look at swap_entry_free.
+*/
+ if (si->flags & SWP_BLKDEV) {
+ struct gendisk *disk = si->bdev->bd_disk;
+
+ if (disk->fops->swap_hint && disk->fops->swap_hint(
+ si->bdev, SWAP_FULL, NULL)) {
+ spin_lock(_avail_lock);
+ WARN_ON(plist_node_empty(>avail_list));
+ plist_del(>avail_list, _avail_head);
+ spin_unlock(_avail_lock);
+ atomic_long_sub(si->pages - si->inuse_pages,
+ _swap_pages);
+ si->full = true;
+ return 0;
+ }
+ }
+
+ /*
* We try to cluster swap pages by allocating them sequentially
* in swap. Once we've allocated SWAPFILE_CLUSTER pages this
* way, however, we resort to first-free allocation, starting
@@ -798,6 +821,14 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
/* free if no reference */
if (!usage) {
bool was_full;
+ struct gendisk *virt_swap = NULL;
+
+ /* Check virtual swap */
+ if (p->flags & SWP_BLKDEV) {
+ virt_swap = p->bdev->bd_disk;
+ if (!virt_swap->fops->swap_hint)
+ virt_swap = NULL;
+ }
dec_cluster_info_page(p, p->cluster_info, offset);
if (offset < p->lowest_bit)
@@ -814,17 +845,18 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
_avail_head);
spin_unlock(_avail_lock);
p->full = false;
+ if (virt_swap)
+ atomic_long_add(p->pages -
+ p->inuse_pages,
+ _swap_pages);
}
atomic_long_inc(_swap_pages);
p->inuse_pages--;
frontswap_invalidate_page(p->type, offset);
- if (p->flags & SWP_BLKDEV) {
- struct gendisk *disk = p->bdev->bd_disk;
- if (disk->fops->swap_hint)
- disk->fops->swap_hint(p->bdev,
- SWAP_FREE, (void *)offset);
- }
+ if (virt_swap)
+ virt_swap->fops->swap_hint(p->bdev,
+ SWAP_FREE, (void *)offset);
}
return usage;
--
2.0.0
--
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[PATCH v1 3/5] mm: VM can be aware of zram fullness
VM uses nr_swap_pages to throttle amount of swap when it reclaims
anonymous pages because the nr_swap_pages means freeable space
of swap disk.
However, it's a problem for zram because zram can limit memory
usage by knob(ie, mem_limit) so that swap out can fail although
VM can see lots of free space from zram disk but no more free
space in zram by the limit. If it happens, VM should notice it
and stop reclaimaing until zram can obtain more free space but
we don't have a way to communicate between VM and zram.
This patch adds new hint SWAP_FULL so that zram can say to VM
I'm full from now on. Then VM cannot reclaim annoymous page
any more. If VM notice swap is full, it can remove swap_info_struct
from swap_avail_head and substract remained freeable space from
nr_swap_pages so that VM can think swap is full until VM frees a
swap and increase nr_swap_pages again.
Signed-off-by: Minchan Kim minc...@kernel.org
---
include/linux/blkdev.h | 1 +
mm/swapfile.c | 44 ++--
2 files changed, 39 insertions(+), 6 deletions(-)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c7220409456c..39f074e0acd7 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1611,6 +1611,7 @@ static inline bool blk_integrity_is_initialized(struct
gendisk *g)
enum swap_blk_hint {
SWAP_FREE,
+ SWAP_FULL,
};
struct block_device_operations {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 209112cf8b83..71e3df0431b6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -493,6 +493,29 @@ static unsigned long scan_swap_map(struct swap_info_struct
*si,
int latency_ration = LATENCY_LIMIT;
/*
+* If zram is full, we don't need to scan and want to stop swap.
+* For it, we removes si from swap_avail_head and decreases
+* nr_swap_pages to prevent further anonymous reclaim so that
+* VM can restart swap out if zram has a free space.
+* Look at swap_entry_free.
+*/
+ if (si-flags SWP_BLKDEV) {
+ struct gendisk *disk = si-bdev-bd_disk;
+
+ if (disk-fops-swap_hint disk-fops-swap_hint(
+ si-bdev, SWAP_FULL, NULL)) {
+ spin_lock(swap_avail_lock);
+ WARN_ON(plist_node_empty(si-avail_list));
+ plist_del(si-avail_list, swap_avail_head);
+ spin_unlock(swap_avail_lock);
+ atomic_long_sub(si-pages - si-inuse_pages,
+ nr_swap_pages);
+ si-full = true;
+ return 0;
+ }
+ }
+
+ /*
* We try to cluster swap pages by allocating them sequentially
* in swap. Once we've allocated SWAPFILE_CLUSTER pages this
* way, however, we resort to first-free allocation, starting
@@ -798,6 +821,14 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
/* free if no reference */
if (!usage) {
bool was_full;
+ struct gendisk *virt_swap = NULL;
+
+ /* Check virtual swap */
+ if (p-flags SWP_BLKDEV) {
+ virt_swap = p-bdev-bd_disk;
+ if (!virt_swap-fops-swap_hint)
+ virt_swap = NULL;
+ }
dec_cluster_info_page(p, p-cluster_info, offset);
if (offset p-lowest_bit)
@@ -814,17 +845,18 @@ static unsigned char swap_entry_free(struct
swap_info_struct *p,
swap_avail_head);
spin_unlock(swap_avail_lock);
p-full = false;
+ if (virt_swap)
+ atomic_long_add(p-pages -
+ p-inuse_pages,
+ nr_swap_pages);
}
atomic_long_inc(nr_swap_pages);
p-inuse_pages--;
frontswap_invalidate_page(p-type, offset);
- if (p-flags SWP_BLKDEV) {
- struct gendisk *disk = p-bdev-bd_disk;
- if (disk-fops-swap_hint)
- disk-fops-swap_hint(p-bdev,
- SWAP_FREE, (void *)offset);
- }
+ if (virt_swap)
+ virt_swap-fops-swap_hint(p-bdev,
+ SWAP_FREE, (void *)offset);
}
return usage;
--
2.0.0
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
