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Message-ID: <20170322000059.GB30149@bbox>
Date: Wed, 22 Mar 2017 09:00:59 +0900
From: Minchan Kim <minchan@...nel.org>
To: <js1304@...il.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
<linux-kernel@...r.kernel.org>, <kernel-team@....com>,
Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH 4/4] zram: make deduplication feature optional
On Thu, Mar 16, 2017 at 11:46:38AM +0900, js1304@...il.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@....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.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....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 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'
> };
> #endif
> --
> 1.9.1
>
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