Re: [PATCH 4/4] zram: make deduplication feature optional

[Joonsoo Kim <iamjoonsoo.kim@lge.com>]

On Wed, Mar 22, 2017 at 09:00:59AM +0900, Minchan Kim wrote:
> On Thu, Mar 16, 2017 at 11:46:38AM +0900, js1304@gmail.com wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> > 
> > Benefit of deduplication is dependent on the workload so it's not
> > preferable to always enable. Therefore, make it optional.
> 
> Please make it to Kconfig, too. And write down the description to impress
> "help a lot for users who uses zram to build output directory"
> And the feature should be disabled as default.

Okay.

> 
> > 
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> > ---
> >  drivers/block/zram/zram_drv.c | 80 ++++++++++++++++++++++++++++++++++++++-----
> >  drivers/block/zram/zram_drv.h |  1 +
> >  2 files changed, 73 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index 012425f..e45aa9f 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -328,6 +328,39 @@ static ssize_t comp_algorithm_store(struct device *dev,
> >  	return len;
> >  }
> >  
> > +static ssize_t use_dedup_show(struct device *dev,
> > +		struct device_attribute *attr, char *buf)
> > +{
> > +	int val;
> > +	struct zram *zram = dev_to_zram(dev);
> > +
> > +	down_read(&zram->init_lock);
> > +	val = zram->use_dedup;
> > +	up_read(&zram->init_lock);
> > +
> > +	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
> > +}
> > +
> > +static ssize_t use_dedup_store(struct device *dev,
> > +		struct device_attribute *attr, const char *buf, size_t len)
> > +{
> > +	int val;
> > +	struct zram *zram = dev_to_zram(dev);
> > +
> > +	if (kstrtoint(buf, 10, &val) || (val != 0 && val != 1))
> > +		return -EINVAL;
> > +
> > +	down_write(&zram->init_lock);
> > +	if (init_done(zram)) {
> > +		up_write(&zram->init_lock);
> > +		pr_info("Can't change dedup usage for initialized device\n");
> > +		return -EBUSY;
> > +	}
> > +	zram->use_dedup = val;
> > +	up_write(&zram->init_lock);
> > +	return len;
> > +}
> > +
> >  static ssize_t compact_store(struct device *dev,
> >  		struct device_attribute *attr, const char *buf, size_t len)
> >  {
> > @@ -422,11 +455,23 @@ static ssize_t debug_stat_show(struct device *dev,
> >  static DEVICE_ATTR_RO(mm_stat);
> >  static DEVICE_ATTR_RO(debug_stat);
> >  
> > -static u32 zram_calc_checksum(unsigned char *mem)
> > +static u32 zram_calc_checksum(struct zram *zram, unsigned char *mem)
> >  {
> > +	if (!zram->use_dedup)
> > +		return 0;
> > +
> 
> Hmm, I don't like this style which every dedup functions have the check
> "use_dedup".
> 
> Can't we abstract like this?

I will try but I'm not sure it can be.

> 
> I want to find more simple way to no need to add the check when new dedup
> functions pop up.
> 
> bool zram_dedup_check
>         if (!zram->dedup)
>                 return false;
> 
>         zram_dedup_checksum
>         entry = zram_dedup_get
>         if (!entry) {
>                 zram_dedup_add
>                 return false;
>         }
>         ..
>         return true;
> 
> 
> zram_bvec_write:
>         ...
>         ...
> 
>         if (zram_dedup_match())
>                 goto found_dup;
> 
> 
> 
> >  	return jhash(mem, PAGE_SIZE, 0);
> >  }
> >  
> > +static unsigned long zram_entry_handle(struct zram *zram,
> > +				struct zram_entry *entry)
> > +{
> > +	if (!zram->use_dedup)
> > +		return (unsigned long)entry;
> > +
> > +	return entry->handle;
> > +}
> > +
> >  static struct zram_entry *zram_entry_alloc(struct zram *zram,
> >  					unsigned int len, gfp_t flags)
> >  {
> > @@ -438,6 +483,9 @@ static struct zram_entry *zram_entry_alloc(struct zram *zram,
> >  	if (!handle)
> >  		return NULL;
> >  
> > +	if (!zram->use_dedup)
> > +		return (struct zram_entry *)handle;
> > +
> >  	entry = kzalloc(sizeof(*entry), flags);
> >  	if (!entry) {
> >  		zs_free(meta->mem_pool, handle);
> > @@ -462,6 +510,9 @@ static void zram_entry_insert(struct zram *zram, struct zram_entry *new,
> >  	struct rb_node **rb_node, *parent = NULL;
> >  	struct zram_entry *entry;
> >  
> > +	if (!zram->use_dedup)
> > +		return;
> > +
> >  	new->checksum = checksum;
> >  	hash = &meta->hash[checksum % meta->hash_size];
> >  	rb_root = &hash->rb_root;
> > @@ -492,7 +543,8 @@ static bool zram_entry_match(struct zram *zram, struct zram_entry *entry,
> >  	struct zram_meta *meta = zram->meta;
> >  	struct zcomp_strm *zstrm;
> >  
> > -	cmem = zs_map_object(meta->mem_pool, entry->handle, ZS_MM_RO);
> > +	cmem = zs_map_object(meta->mem_pool,
> > +			zram_entry_handle(zram, entry), ZS_MM_RO);
> >  	if (entry->len == PAGE_SIZE) {
> >  		match = !memcmp(mem, cmem, PAGE_SIZE);
> >  	} else {
> > @@ -501,7 +553,7 @@ static bool zram_entry_match(struct zram *zram, struct zram_entry *entry,
> >  			match = !memcmp(mem, zstrm->buffer, PAGE_SIZE);
> >  		zcomp_stream_put(zram->comp);
> >  	}
> > -	zs_unmap_object(meta->mem_pool, entry->handle);
> > +	zs_unmap_object(meta->mem_pool, zram_entry_handle(zram, entry));
> >  
> >  	return match;
> >  }
> > @@ -521,6 +573,11 @@ static bool zram_entry_put(struct zram *zram, struct zram_meta *meta,
> >  	struct zram_hash *hash;
> >  	u32 checksum;
> >  
> > +	if (!zram->use_dedup) {
> > +		zs_free(meta->mem_pool, zram_entry_handle(zram, entry));
> > +		return false;
> > +	}
> > +
> >  	if (!populated)
> >  		goto free;
> >  
> > @@ -551,6 +608,9 @@ static struct zram_entry *zram_entry_get(struct zram *zram,
> >  	struct zram_entry *entry;
> >  	struct rb_node *rb_node;
> >  
> > +	if (!zram->use_dedup)
> > +		return NULL;
> > +
> >  	hash = &meta->hash[checksum % meta->hash_size];
> >  
> >  	spin_lock(&hash->lock);
> > @@ -713,7 +773,8 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
> >  		return 0;
> >  	}
> >  
> > -	cmem = zs_map_object(meta->mem_pool, entry->handle, ZS_MM_RO);
> > +	cmem = zs_map_object(meta->mem_pool,
> > +			zram_entry_handle(zram, entry), ZS_MM_RO);
> >  	if (size == PAGE_SIZE) {
> >  		copy_page(mem, cmem);
> >  	} else {
> > @@ -722,7 +783,7 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
> >  		ret = zcomp_decompress(zstrm, cmem, size, mem);
> >  		zcomp_stream_put(zram->comp);
> >  	}
> > -	zs_unmap_object(meta->mem_pool, entry->handle);
> > +	zs_unmap_object(meta->mem_pool, zram_entry_handle(zram, entry));
> >  	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
> >  
> >  	/* Should NEVER happen. Return bio error if it does. */
> > @@ -840,7 +901,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> >  		goto out;
> >  	}
> >  
> > -	checksum = zram_calc_checksum(uncmem);
> > +	checksum = zram_calc_checksum(zram, uncmem);
> >  	if (!entry) {
> >  		entry = zram_entry_get(zram, uncmem, checksum);
> >  		if (entry) {
> > @@ -915,7 +976,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> >  		goto out;
> >  	}
> >  
> > -	cmem = zs_map_object(meta->mem_pool, entry->handle, ZS_MM_WO);
> > +	cmem = zs_map_object(meta->mem_pool,
> > +			zram_entry_handle(zram, entry), ZS_MM_WO);
> >  
> >  	if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
> >  		src = kmap_atomic(page);
> > @@ -927,7 +989,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> >  
> >  	zcomp_stream_put(zram->comp);
> >  	zstrm = NULL;
> > -	zs_unmap_object(meta->mem_pool, entry->handle);
> > +	zs_unmap_object(meta->mem_pool, zram_entry_handle(zram, entry));
> >  	zram_entry_insert(zram, entry, checksum);
> >  
> >  found_duplication:
> > @@ -1310,6 +1372,7 @@ static int zram_open(struct block_device *bdev, fmode_t mode)
> >  static DEVICE_ATTR_WO(mem_used_max);
> >  static DEVICE_ATTR_RW(max_comp_streams);
> >  static DEVICE_ATTR_RW(comp_algorithm);
> > +static DEVICE_ATTR_RW(use_dedup);
> >  
> >  static struct attribute *zram_disk_attrs[] = {
> >  	&dev_attr_disksize.attr,
> > @@ -1320,6 +1383,7 @@ static int zram_open(struct block_device *bdev, fmode_t mode)
> >  	&dev_attr_mem_used_max.attr,
> >  	&dev_attr_max_comp_streams.attr,
> >  	&dev_attr_comp_algorithm.attr,
> > +	&dev_attr_use_dedup.attr,
> >  	&dev_attr_io_stat.attr,
> >  	&dev_attr_mm_stat.attr,
> >  	&dev_attr_debug_stat.attr,
> > diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> > index 07d1f8d..b823555 100644
> > --- a/drivers/block/zram/zram_drv.h
> > +++ b/drivers/block/zram/zram_drv.h
> > @@ -141,5 +141,6 @@ struct zram {
> >  	 * zram is claimed so open request will be failed
> >  	 */
> >  	bool claim; /* Protected by bdev->bd_mutex */
> > +	int use_dedup;
> 
> For binary result, I want to use 'bool'

Okay.

Thanks.