| Message ID | 20230727080502.77895-29-zhengqi.arch@bytedance.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | use refcount+RCU method to implement lockless slab shrink | expand |
On 7/27/23 17:04, Qi Zheng wrote: > In preparation for implementing lockless slab shrink, use new APIs to > dynamically allocate the dm-zoned-meta shrinker, so that it can be freed > asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU > read-side critical section when releasing the struct dmz_metadata. > > Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> > Reviewed-by: Muchun Song <songmuchun@bytedance.com> > --- > drivers/md/dm-zoned-metadata.c | 28 ++++++++++++++++------------ > 1 file changed, 16 insertions(+), 12 deletions(-) > > diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c > index 9d3cca8e3dc9..0bcb26a43578 100644 > --- a/drivers/md/dm-zoned-metadata.c > +++ b/drivers/md/dm-zoned-metadata.c > @@ -187,7 +187,7 @@ struct dmz_metadata { > struct rb_root mblk_rbtree; > struct list_head mblk_lru_list; > struct list_head mblk_dirty_list; > - struct shrinker mblk_shrinker; > + struct shrinker *mblk_shrinker; > > /* Zone allocation management */ > struct mutex map_lock; > @@ -615,7 +615,7 @@ static unsigned long dmz_shrink_mblock_cache(struct dmz_metadata *zmd, > static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink, > struct shrink_control *sc) > { > - struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker); > + struct dmz_metadata *zmd = shrink->private_data; > > return atomic_read(&zmd->nr_mblks); > } > @@ -626,7 +626,7 @@ static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink, > static unsigned long dmz_mblock_shrinker_scan(struct shrinker *shrink, > struct shrink_control *sc) > { > - struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker); > + struct dmz_metadata *zmd = shrink->private_data; > unsigned long count; > > spin_lock(&zmd->mblk_lock); > @@ -2936,19 +2936,23 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev, > */ > zmd->min_nr_mblks = 2 + zmd->nr_map_blocks + zmd->zone_nr_bitmap_blocks * 16; > zmd->max_nr_mblks = zmd->min_nr_mblks + 512; > - zmd->mblk_shrinker.count_objects = dmz_mblock_shrinker_count; > - zmd->mblk_shrinker.scan_objects = dmz_mblock_shrinker_scan; > - zmd->mblk_shrinker.seeks = DEFAULT_SEEKS; > > /* Metadata cache shrinker */ > - ret = register_shrinker(&zmd->mblk_shrinker, "dm-zoned-meta:(%u:%u)", > - MAJOR(dev->bdev->bd_dev), > - MINOR(dev->bdev->bd_dev)); > - if (ret) { > - dmz_zmd_err(zmd, "Register metadata cache shrinker failed"); > + zmd->mblk_shrinker = shrinker_alloc(0, "dm-zoned-meta:(%u:%u)", > + MAJOR(dev->bdev->bd_dev), > + MINOR(dev->bdev->bd_dev)); > + if (!zmd->mblk_shrinker) { > + dmz_zmd_err(zmd, "Allocate metadata cache shrinker failed"); ret is not set here, so dmz_ctr_metadata() will return success. You need to add: ret = -ENOMEM; or something. > goto err; > } > > + zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count; > + zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan; > + zmd->mblk_shrinker->seeks = DEFAULT_SEEKS; > + zmd->mblk_shrinker->private_data = zmd; > + > + shrinker_register(zmd->mblk_shrinker); I fail to see how this new shrinker API is better... Why isn't there a shrinker_alloc_and_register() function ? That would avoid adding all this code all over the place as the new API call would be very similar to the current shrinker_register() call with static allocation. > + > dmz_zmd_info(zmd, "DM-Zoned metadata version %d", zmd->sb_version); > for (i = 0; i < zmd->nr_devs; i++) > dmz_print_dev(zmd, i); > @@ -2995,7 +2999,7 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev, > */ > void dmz_dtr_metadata(struct dmz_metadata *zmd) > { > - unregister_shrinker(&zmd->mblk_shrinker); > + shrinker_free(zmd->mblk_shrinker); > dmz_cleanup_metadata(zmd); > kfree(zmd); > }
Hi, On 2023/7/27 16:30, Damien Le Moal wrote: > On 7/27/23 17:04, Qi Zheng wrote: >> In preparation for implementing lockless slab shrink, use new APIs to >> dynamically allocate the dm-zoned-meta shrinker, so that it can be freed >> asynchronously using kfree_rcu(). Then it doesn't need to wait for RCU >> read-side critical section when releasing the struct dmz_metadata. >> >> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> >> Reviewed-by: Muchun Song <songmuchun@bytedance.com> >> --- >> drivers/md/dm-zoned-metadata.c | 28 ++++++++++++++++------------ >> 1 file changed, 16 insertions(+), 12 deletions(-) >> >> diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c >> index 9d3cca8e3dc9..0bcb26a43578 100644 >> --- a/drivers/md/dm-zoned-metadata.c >> +++ b/drivers/md/dm-zoned-metadata.c >> @@ -187,7 +187,7 @@ struct dmz_metadata { >> struct rb_root mblk_rbtree; >> struct list_head mblk_lru_list; >> struct list_head mblk_dirty_list; >> - struct shrinker mblk_shrinker; >> + struct shrinker *mblk_shrinker; >> >> /* Zone allocation management */ >> struct mutex map_lock; >> @@ -615,7 +615,7 @@ static unsigned long dmz_shrink_mblock_cache(struct dmz_metadata *zmd, >> static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink, >> struct shrink_control *sc) >> { >> - struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker); >> + struct dmz_metadata *zmd = shrink->private_data; >> >> return atomic_read(&zmd->nr_mblks); >> } >> @@ -626,7 +626,7 @@ static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink, >> static unsigned long dmz_mblock_shrinker_scan(struct shrinker *shrink, >> struct shrink_control *sc) >> { >> - struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker); >> + struct dmz_metadata *zmd = shrink->private_data; >> unsigned long count; >> >> spin_lock(&zmd->mblk_lock); >> @@ -2936,19 +2936,23 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev, >> */ >> zmd->min_nr_mblks = 2 + zmd->nr_map_blocks + zmd->zone_nr_bitmap_blocks * 16; >> zmd->max_nr_mblks = zmd->min_nr_mblks + 512; >> - zmd->mblk_shrinker.count_objects = dmz_mblock_shrinker_count; >> - zmd->mblk_shrinker.scan_objects = dmz_mblock_shrinker_scan; >> - zmd->mblk_shrinker.seeks = DEFAULT_SEEKS; >> >> /* Metadata cache shrinker */ >> - ret = register_shrinker(&zmd->mblk_shrinker, "dm-zoned-meta:(%u:%u)", >> - MAJOR(dev->bdev->bd_dev), >> - MINOR(dev->bdev->bd_dev)); >> - if (ret) { >> - dmz_zmd_err(zmd, "Register metadata cache shrinker failed"); >> + zmd->mblk_shrinker = shrinker_alloc(0, "dm-zoned-meta:(%u:%u)", >> + MAJOR(dev->bdev->bd_dev), >> + MINOR(dev->bdev->bd_dev)); >> + if (!zmd->mblk_shrinker) { >> + dmz_zmd_err(zmd, "Allocate metadata cache shrinker failed"); > > ret is not set here, so dmz_ctr_metadata() will return success. You need to add: > ret = -ENOMEM; > or something. Indeed, will fix. >> goto err; >> } >> >> + zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count; >> + zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan; >> + zmd->mblk_shrinker->seeks = DEFAULT_SEEKS; >> + zmd->mblk_shrinker->private_data = zmd; >> + >> + shrinker_register(zmd->mblk_shrinker); > > I fail to see how this new shrinker API is better... Why isn't there a > shrinker_alloc_and_register() function ? That would avoid adding all this code > all over the place as the new API call would be very similar to the current > shrinker_register() call with static allocation. In some registration scenarios, memory needs to be allocated in advance. So we continue to use the previous prealloc/register_prepared() algorithm. The shrinker_alloc_and_register() is just a helper function that combines the two, and this increases the number of APIs that shrinker exposes to the outside, so I choose not to add this helper. Thanks, Qi > >> + >> dmz_zmd_info(zmd, "DM-Zoned metadata version %d", zmd->sb_version); >> for (i = 0; i < zmd->nr_devs; i++) >> dmz_print_dev(zmd, i); >> @@ -2995,7 +2999,7 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev, >> */ >> void dmz_dtr_metadata(struct dmz_metadata *zmd) >> { >> - unregister_shrinker(&zmd->mblk_shrinker); >> + shrinker_free(zmd->mblk_shrinker); >> dmz_cleanup_metadata(zmd); >> kfree(zmd); >> } >
On 7/27/23 17:55, Qi Zheng wrote: >>> goto err; >>> } >>> + zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count; >>> + zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan; >>> + zmd->mblk_shrinker->seeks = DEFAULT_SEEKS; >>> + zmd->mblk_shrinker->private_data = zmd; >>> + >>> + shrinker_register(zmd->mblk_shrinker); >> >> I fail to see how this new shrinker API is better... Why isn't there a >> shrinker_alloc_and_register() function ? That would avoid adding all this code >> all over the place as the new API call would be very similar to the current >> shrinker_register() call with static allocation. > > In some registration scenarios, memory needs to be allocated in advance. > So we continue to use the previous prealloc/register_prepared() > algorithm. The shrinker_alloc_and_register() is just a helper function > that combines the two, and this increases the number of APIs that > shrinker exposes to the outside, so I choose not to add this helper. And that results in more code in many places instead of less code + a simple inline helper in the shrinker header file... So not adding that super simple helper is not exactly the best choice in my opinion.
On 2023/7/27 18:20, Damien Le Moal wrote: > On 7/27/23 17:55, Qi Zheng wrote: >>>> goto err; >>>> } >>>> + zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count; >>>> + zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan; >>>> + zmd->mblk_shrinker->seeks = DEFAULT_SEEKS; >>>> + zmd->mblk_shrinker->private_data = zmd; >>>> + >>>> + shrinker_register(zmd->mblk_shrinker); >>> >>> I fail to see how this new shrinker API is better... Why isn't there a >>> shrinker_alloc_and_register() function ? That would avoid adding all this code >>> all over the place as the new API call would be very similar to the current >>> shrinker_register() call with static allocation. >> >> In some registration scenarios, memory needs to be allocated in advance. >> So we continue to use the previous prealloc/register_prepared() >> algorithm. The shrinker_alloc_and_register() is just a helper function >> that combines the two, and this increases the number of APIs that >> shrinker exposes to the outside, so I choose not to add this helper. > > And that results in more code in many places instead of less code + a simple > inline helper in the shrinker header file... So not adding that super simple It also needs to be exported to the driver for use. > helper is not exactly the best choice in my opinion. Hm, either one is fine for me. If no one else objects, I can add this helper. ;) >
On Thu, Jul 27, 2023 at 07:20:46PM +0900, Damien Le Moal wrote: > On 7/27/23 17:55, Qi Zheng wrote: > >>> goto err; > >>> } > >>> + zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count; > >>> + zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan; > >>> + zmd->mblk_shrinker->seeks = DEFAULT_SEEKS; > >>> + zmd->mblk_shrinker->private_data = zmd; > >>> + > >>> + shrinker_register(zmd->mblk_shrinker); > >> > >> I fail to see how this new shrinker API is better... Why isn't there a > >> shrinker_alloc_and_register() function ? That would avoid adding all this code > >> all over the place as the new API call would be very similar to the current > >> shrinker_register() call with static allocation. > > > > In some registration scenarios, memory needs to be allocated in advance. > > So we continue to use the previous prealloc/register_prepared() > > algorithm. The shrinker_alloc_and_register() is just a helper function > > that combines the two, and this increases the number of APIs that > > shrinker exposes to the outside, so I choose not to add this helper. > > And that results in more code in many places instead of less code + a simple > inline helper in the shrinker header file... It's not just a "simple helper" - it's a function that has to take 6 or 7 parameters with a return value that must be checked and handled. This was done in the first versions of the patch set - the amount of code in each caller does not go down and, IMO, was much harder to read and determine "this is obviously correct" that what we have now. > So not adding that super simple > helper is not exactly the best choice in my opinion. Each to their own - I much prefer the existing style/API over having to go look up a helper function every time I want to check some random shrinker has been set up correctly.... -Dave.
On 7/28/23 07:59, Dave Chinner wrote: > On Thu, Jul 27, 2023 at 07:20:46PM +0900, Damien Le Moal wrote: >> On 7/27/23 17:55, Qi Zheng wrote: >>>>> goto err; >>>>> } >>>>> + zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count; >>>>> + zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan; >>>>> + zmd->mblk_shrinker->seeks = DEFAULT_SEEKS; >>>>> + zmd->mblk_shrinker->private_data = zmd; >>>>> + >>>>> + shrinker_register(zmd->mblk_shrinker); >>>> >>>> I fail to see how this new shrinker API is better... Why isn't there a >>>> shrinker_alloc_and_register() function ? That would avoid adding all this code >>>> all over the place as the new API call would be very similar to the current >>>> shrinker_register() call with static allocation. >>> >>> In some registration scenarios, memory needs to be allocated in advance. >>> So we continue to use the previous prealloc/register_prepared() >>> algorithm. The shrinker_alloc_and_register() is just a helper function >>> that combines the two, and this increases the number of APIs that >>> shrinker exposes to the outside, so I choose not to add this helper. >> >> And that results in more code in many places instead of less code + a simple >> inline helper in the shrinker header file... > > It's not just a "simple helper" - it's a function that has to take 6 > or 7 parameters with a return value that must be checked and > handled. > > This was done in the first versions of the patch set - the amount of > code in each caller does not go down and, IMO, was much harder to > read and determine "this is obviously correct" that what we have > now. > >> So not adding that super simple >> helper is not exactly the best choice in my opinion. > > Each to their own - I much prefer the existing style/API over having > to go look up a helper function every time I want to check some > random shrinker has been set up correctly.... OK. All fair points.
diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c index 9d3cca8e3dc9..0bcb26a43578 100644 --- a/drivers/md/dm-zoned-metadata.c +++ b/drivers/md/dm-zoned-metadata.c @@ -187,7 +187,7 @@ struct dmz_metadata { struct rb_root mblk_rbtree; struct list_head mblk_lru_list; struct list_head mblk_dirty_list; - struct shrinker mblk_shrinker; + struct shrinker *mblk_shrinker; /* Zone allocation management */ struct mutex map_lock; @@ -615,7 +615,7 @@ static unsigned long dmz_shrink_mblock_cache(struct dmz_metadata *zmd, static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink, struct shrink_control *sc) { - struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker); + struct dmz_metadata *zmd = shrink->private_data; return atomic_read(&zmd->nr_mblks); } @@ -626,7 +626,7 @@ static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink, static unsigned long dmz_mblock_shrinker_scan(struct shrinker *shrink, struct shrink_control *sc) { - struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker); + struct dmz_metadata *zmd = shrink->private_data; unsigned long count; spin_lock(&zmd->mblk_lock); @@ -2936,19 +2936,23 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev, */ zmd->min_nr_mblks = 2 + zmd->nr_map_blocks + zmd->zone_nr_bitmap_blocks * 16; zmd->max_nr_mblks = zmd->min_nr_mblks + 512; - zmd->mblk_shrinker.count_objects = dmz_mblock_shrinker_count; - zmd->mblk_shrinker.scan_objects = dmz_mblock_shrinker_scan; - zmd->mblk_shrinker.seeks = DEFAULT_SEEKS; /* Metadata cache shrinker */ - ret = register_shrinker(&zmd->mblk_shrinker, "dm-zoned-meta:(%u:%u)", - MAJOR(dev->bdev->bd_dev), - MINOR(dev->bdev->bd_dev)); - if (ret) { - dmz_zmd_err(zmd, "Register metadata cache shrinker failed"); + zmd->mblk_shrinker = shrinker_alloc(0, "dm-zoned-meta:(%u:%u)", + MAJOR(dev->bdev->bd_dev), + MINOR(dev->bdev->bd_dev)); + if (!zmd->mblk_shrinker) { + dmz_zmd_err(zmd, "Allocate metadata cache shrinker failed"); goto err; } + zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count; + zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan; + zmd->mblk_shrinker->seeks = DEFAULT_SEEKS; + zmd->mblk_shrinker->private_data = zmd; + + shrinker_register(zmd->mblk_shrinker); + dmz_zmd_info(zmd, "DM-Zoned metadata version %d", zmd->sb_version); for (i = 0; i < zmd->nr_devs; i++) dmz_print_dev(zmd, i); @@ -2995,7 +2999,7 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev, */ void dmz_dtr_metadata(struct dmz_metadata *zmd) { - unregister_shrinker(&zmd->mblk_shrinker); + shrinker_free(zmd->mblk_shrinker); dmz_cleanup_metadata(zmd); kfree(zmd); }