zram: make compression algorithm selection possible (e46b8a03) · Commits · 戴 / test

Documentation/ABI/testing/sysfs-block-zram

+8 −0

Original line number	Diff line number	Diff line
		@@ -65,6 +65,14 @@ Description:
		number of backend's zcomp_strm compression streams (number of
		concurrent compress operations).

		What: /sys/block/zram<id>/comp_algorithm
		Date: February 2014
		Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
		Description:
		The comp_algorithm file is read-write and lets to show
		available and selected compression algorithms, change
		compression algorithm selection.

		What: /sys/block/zram<id>/notify_free
		Date: August 2010
		Contact: Nitin Gupta <ngupta@vflare.org>

Documentation/blockdev/zram.txt

+19 −5

Original line number	Diff line number	Diff line
		@@ -42,7 +42,21 @@ will not take any effect, because single stream compression backend implemented
		as a special case and does not support dynamic max_comp_streams. Only multi
		stream backend supports dynamic max_comp_streams adjustment.

		3) Set Disksize
		3) Select compression algorithm
		Using comp_algorithm device attribute one can see available and
		currently selected (shown in square brackets) compression algortithms,
		change selected compression algorithm (once the device is initialised
		there is no way to change compression algorithm).

		Examples:
		#show supported compression algorithms
		cat /sys/block/zram0/comp_algorithm
		lzo [lz4]

		#select lzo compression algorithm
		echo lzo > /sys/block/zram0/comp_algorithm

		4) Set Disksize
		Set disk size by writing the value to sysfs node 'disksize'.
		The value can be either in bytes or you can use mem suffixes.
		Examples:
		@@ -59,14 +73,14 @@ There is little point creating a zram of greater than twice the size of memory
		since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the
		size of the disk when not in use so a huge zram is wasteful.

		4) Activate:
		5) Activate:
		mkswap /dev/zram0
		swapon /dev/zram0

		mkfs.ext4 /dev/zram1
		mount /dev/zram1 /tmp

		5) Stats:
		6) Stats:
		Per-device statistics are exported as various nodes under
		/sys/block/zram<id>/
		disksize
		@@ -81,11 +95,11 @@ size of the disk when not in use so a huge zram is wasteful.
		compr_data_size
		mem_used_total

		6) Deactivate:
		7) Deactivate:
		swapoff /dev/zram0
		umount /dev/zram1

		7) Reset:
		8) Reset:
		Write any positive value to 'reset' sysfs node
		echo 1 > /sys/block/zram0/reset
		echo 1 > /sys/block/zram1/reset

drivers/block/zram/zcomp.c

+29 −3

Original line number	Diff line number	Diff line
		@@ -39,11 +39,20 @@ struct zcomp_strm_multi {
		wait_queue_head_t strm_wait;
		};

		static struct zcomp_backend *backends[] = {
		&zcomp_lzo,
		NULL
		};

		static struct zcomp_backend find_backend(const char compress)
		{
		if (strncmp(compress, "lzo", 3) == 0)
		return &zcomp_lzo;
		return NULL;
		int i = 0;
		while (backends[i]) {
		if (sysfs_streq(compress, backends[i]->name))
		break;
		i++;
		}
		return backends[i];
		}

		static void zcomp_strm_free(struct zcomp comp, struct zcomp_strm zstrm)
		@@ -251,6 +260,23 @@ static int zcomp_strm_single_create(struct zcomp *comp)
		return 0;
		}

		/* show available compressors */
		ssize_t zcomp_available_show(const char comp, char buf)
		{
		ssize_t sz = 0;
		int i = 0;

		while (backends[i]) {
		if (sysfs_streq(comp, backends[i]->name))
		sz += sprintf(buf + sz, "[%s] ", backends[i]->name);
		else
		sz += sprintf(buf + sz, "%s ", backends[i]->name);
		i++;
		}
		sz += sprintf(buf + sz, "\n");
		return sz;
		}

		int zcomp_set_max_streams(struct zcomp *comp, int num_strm)
		{
		return comp->set_max_streams(comp, num_strm);

drivers/block/zram/zcomp.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -50,6 +50,8 @@ struct zcomp {
		void (destroy)(struct zcomp comp);
		};

		ssize_t zcomp_available_show(const char comp, char buf);

		struct zcomp zcomp_create(const char comp, int max_strm);
		void zcomp_destroy(struct zcomp *comp);

drivers/block/zram/zram_drv.c

+34 −3

Original line number	Diff line number	Diff line
		@@ -141,6 +141,34 @@ static ssize_t max_comp_streams_store(struct device *dev,
		return len;
		}

		static ssize_t comp_algorithm_show(struct device *dev,
		struct device_attribute attr, char buf)
		{
		size_t sz;
		struct zram *zram = dev_to_zram(dev);

		down_read(&zram->init_lock);
		sz = zcomp_available_show(zram->compressor, buf);
		up_read(&zram->init_lock);

		return sz;
		}

		static ssize_t comp_algorithm_store(struct device *dev,
		struct device_attribute attr, const char buf, size_t len)
		{
		struct zram *zram = dev_to_zram(dev);
		down_write(&zram->init_lock);
		if (init_done(zram)) {
		up_write(&zram->init_lock);
		pr_info("Can't change algorithm for initialized device\n");
		return -EBUSY;
		}
		strlcpy(zram->compressor, buf, sizeof(zram->compressor));
		up_write(&zram->init_lock);
		return len;
		}

		/* flag operations needs meta->tb_lock */
		static int zram_test_flag(struct zram_meta *meta, u32 index,
		enum zram_pageflags flag)
		@@ -572,10 +600,10 @@ static ssize_t disksize_store(struct device *dev,
		goto out_free_meta;
		}

		zram->comp = zcomp_create(default_compressor, zram->max_comp_streams);
		zram->comp = zcomp_create(zram->compressor, zram->max_comp_streams);
		if (!zram->comp) {
		pr_info("Cannot initialise %s compressing backend\n",
		default_compressor);
		zram->compressor);
		err = -EINVAL;
		goto out_free_meta;
		}
		@@ -735,6 +763,8 @@ static DEVICE_ATTR(orig_data_size, S_IRUGO, orig_data_size_show, NULL);
		static DEVICE_ATTR(mem_used_total, S_IRUGO, mem_used_total_show, NULL);
		static DEVICE_ATTR(max_comp_streams, S_IRUGO \| S_IWUSR,
		max_comp_streams_show, max_comp_streams_store);
		static DEVICE_ATTR(comp_algorithm, S_IRUGO \| S_IWUSR,
		comp_algorithm_show, comp_algorithm_store);

		ZRAM_ATTR_RO(num_reads);
		ZRAM_ATTR_RO(num_writes);
		@@ -760,6 +790,7 @@ static struct attribute *zram_disk_attrs[] = {
		&dev_attr_compr_data_size.attr,
		&dev_attr_mem_used_total.attr,
		&dev_attr_max_comp_streams.attr,
		&dev_attr_comp_algorithm.attr,
		NULL,
		};

		@@ -820,7 +851,7 @@ static int create_device(struct zram *zram, int device_id)
		pr_warn("Error creating sysfs group");
		goto out_free_disk;
		}

		strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
		zram->meta = NULL;
		zram->max_comp_streams = 1;
		return 0;

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