Commit bb8b93b5 authored by Maciej S. Szmigiero's avatar Maciej S. Szmigiero Committed by Linus Torvalds
Browse files

mm/zswap: allow setting default status, compressor and allocator in Kconfig 



The compressed cache for swap pages (zswap) currently needs from 1 to 3
extra kernel command line parameters in order to make it work: it has to
be enabled by adding a "zswap.enabled=1" command line parameter and if one
wants a different compressor or pool allocator than the default lzo / zbud
combination then these choices also need to be specified on the kernel
command line in additional parameters.

Using a different compressor and allocator for zswap is actually pretty
common as guides often recommend using the lz4 / z3fold pair instead of
the default one.  In such case it is also necessary to remember to enable
the appropriate compression algorithm and pool allocator in the kernel
config manually.

Let's avoid the need for adding these kernel command line parameters and
automatically pull in the dependencies for the selected compressor
algorithm and pool allocator by adding an appropriate default switches to
Kconfig.

The default values for these options match what the code was using
previously as its defaults.

Signed-off-by: default avatarMaciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarVitaly Wool <vitaly.wool@konsulko.com>
Link: http://lkml.kernel.org/r/20200202000112.456103-1-mail@maciej.szmigiero.name


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4708f318

Documentation/vm/zswap.rst

+12 −8
Original line number Diff line number Diff line
@@ -35,9 +35,11 @@ Zswap evicts pages from compressed cache on an LRU basis to the backing swap 
device when the compressed pool reaches its size limit.  This requirement had

been identified in prior community discussions.



Zswap is disabled by default but can be enabled at boot time by setting

the ``enabled`` attribute to 1 at boot time. ie: ``zswap.enabled=1``.  Zswap

can also be enabled and disabled at runtime using the sysfs interface.

Whether Zswap is enabled at the boot time depends on whether

the ``CONFIG_ZSWAP_DEFAULT_ON`` Kconfig option is enabled or not.

This setting can then be overridden by providing the kernel command line

``zswap.enabled=`` option, for example ``zswap.enabled=0``.

Zswap can also be enabled and disabled at runtime using the sysfs interface.

An example command to enable zswap at runtime, assuming sysfs is mounted

at ``/sys``, is::
@@ -64,9 +66,10 @@ allocation in zpool is not directly accessible by address. Rather, a handle is 
returned by the allocation routine and that handle must be mapped before being

accessed.  The compressed memory pool grows on demand and shrinks as compressed

pages are freed.  The pool is not preallocated.  By default, a zpool

of type zbud is created, but it can be selected at boot time by

setting the ``zpool`` attribute, e.g. ``zswap.zpool=zbud``. It can

also be changed at runtime using the sysfs ``zpool`` attribute, e.g.::

of type selected in ``CONFIG_ZSWAP_ZPOOL_DEFAULT`` Kconfig option is created,

but it can be overridden at boot time by setting the ``zpool`` attribute,

e.g. ``zswap.zpool=zbud``. It can also be changed at runtime using the sysfs

``zpool`` attribute, e.g.::



	echo zbud > /sys/module/zswap/parameters/zpool
@@ -97,8 +100,9 @@ controlled policy: 
* max_pool_percent - The maximum percentage of memory that the compressed

  pool can occupy.



The default compressor is lzo, but it can be selected at boot time by

setting the ``compressor`` attribute, e.g. ``zswap.compressor=lzo``.

The default compressor is selected in ``CONFIG_ZSWAP_COMPRESSOR_DEFAULT``

Kconfig option, but it can be overridden at boot time by setting the

``compressor`` attribute, e.g. ``zswap.compressor=lzo``.

It can also be changed at runtime using the sysfs "compressor"

attribute, e.g.::

mm/Kconfig

+117 −1
Original line number Diff line number Diff line
@@ -533,7 +533,6 @@ config MEM_SOFT_DIRTY 
config ZSWAP

	bool "Compressed cache for swap pages (EXPERIMENTAL)"

	depends on FRONTSWAP && CRYPTO=y

	select CRYPTO_LZO

	select ZPOOL

	help

	  A lightweight compressed cache for swap pages.  It takes
@@ -549,6 +548,123 @@ config ZSWAP 
	  they have not be fully explored on the large set of potential

	  configurations and workloads that exist.



choice

	prompt "Compressed cache for swap pages default compressor"

	depends on ZSWAP

	default ZSWAP_COMPRESSOR_DEFAULT_LZO

	help

	  Selects the default compression algorithm for the compressed cache

	  for swap pages.



	  For an overview what kind of performance can be expected from

	  a particular compression algorithm please refer to the benchmarks

	  available at the following LWN page:

	  https://lwn.net/Articles/751795/



	  If in doubt, select 'LZO'.



	  The selection made here can be overridden by using the kernel

	  command line 'zswap.compressor=' option.



config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE

	bool "Deflate"

	select CRYPTO_DEFLATE

	help

	  Use the Deflate algorithm as the default compression algorithm.



config ZSWAP_COMPRESSOR_DEFAULT_LZO

	bool "LZO"

	select CRYPTO_LZO

	help

	  Use the LZO algorithm as the default compression algorithm.



config ZSWAP_COMPRESSOR_DEFAULT_842

	bool "842"

	select CRYPTO_842

	help

	  Use the 842 algorithm as the default compression algorithm.



config ZSWAP_COMPRESSOR_DEFAULT_LZ4

	bool "LZ4"

	select CRYPTO_LZ4

	help

	  Use the LZ4 algorithm as the default compression algorithm.



config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC

	bool "LZ4HC"

	select CRYPTO_LZ4HC

	help

	  Use the LZ4HC algorithm as the default compression algorithm.



config ZSWAP_COMPRESSOR_DEFAULT_ZSTD

	bool "zstd"

	select CRYPTO_ZSTD

	help

	  Use the zstd algorithm as the default compression algorithm.

endchoice



config ZSWAP_COMPRESSOR_DEFAULT

       string

       depends on ZSWAP

       default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE

       default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO

       default "842" if ZSWAP_COMPRESSOR_DEFAULT_842

       default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4

       default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC

       default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD

       default ""



choice

	prompt "Compressed cache for swap pages default allocator"

	depends on ZSWAP

	default ZSWAP_ZPOOL_DEFAULT_ZBUD

	help

	  Selects the default allocator for the compressed cache for

	  swap pages.

	  The default is 'zbud' for compatibility, however please do

	  read the description of each of the allocators below before

	  making a right choice.



	  The selection made here can be overridden by using the kernel

	  command line 'zswap.zpool=' option.



config ZSWAP_ZPOOL_DEFAULT_ZBUD

	bool "zbud"

	select ZBUD

	help

	  Use the zbud allocator as the default allocator.



config ZSWAP_ZPOOL_DEFAULT_Z3FOLD

	bool "z3fold"

	select Z3FOLD

	help

	  Use the z3fold allocator as the default allocator.



config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC

	bool "zsmalloc"

	select ZSMALLOC

	help

	  Use the zsmalloc allocator as the default allocator.

endchoice



config ZSWAP_ZPOOL_DEFAULT

       string

       depends on ZSWAP

       default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD

       default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD

       default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC

       default ""



config ZSWAP_DEFAULT_ON

	bool "Enable the compressed cache for swap pages by default"

	depends on ZSWAP

	help

	  If selected, the compressed cache for swap pages will be enabled

	  at boot, otherwise it will be disabled.



	  The selection made here can be overridden by using the kernel

	  command line 'zswap.enabled=' option.



config ZPOOL

	tristate "Common API for compressed memory storage"

	help

mm/zswap.c

+12 −12
Original line number Diff line number Diff line
@@ -77,8 +77,8 @@ static bool zswap_pool_reached_full; 


#define ZSWAP_PARAM_UNSET ""



/* Enable/disable zswap (disabled by default) */

static bool zswap_enabled;

/* Enable/disable zswap */

static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON);

static int zswap_enabled_param_set(const char *,

				   const struct kernel_param *);

static struct kernel_param_ops zswap_enabled_param_ops = {
@@ -88,8 +88,7 @@ static struct kernel_param_ops zswap_enabled_param_ops = { 
module_param_cb(enabled, &zswap_enabled_param_ops, &zswap_enabled, 0644);



/* Crypto compressor to use */

#define ZSWAP_COMPRESSOR_DEFAULT "lzo"

static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;

static char *zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;

static int zswap_compressor_param_set(const char *,

				      const struct kernel_param *);

static struct kernel_param_ops zswap_compressor_param_ops = {
@@ -101,8 +100,7 @@ module_param_cb(compressor, &zswap_compressor_param_ops, 
		&zswap_compressor, 0644);



/* Compressed storage zpool to use */

#define ZSWAP_ZPOOL_DEFAULT "zbud"

static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;

static char *zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;

static int zswap_zpool_param_set(const char *, const struct kernel_param *);

static struct kernel_param_ops zswap_zpool_param_ops = {

	.set =		zswap_zpool_param_set,
@@ -599,11 +597,12 @@ static __init struct zswap_pool *__zswap_pool_create_fallback(void) 
	bool has_comp, has_zpool;



	has_comp = crypto_has_comp(zswap_compressor, 0, 0);

	if (!has_comp && strcmp(zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT)) {

	if (!has_comp && strcmp(zswap_compressor,

				CONFIG_ZSWAP_COMPRESSOR_DEFAULT)) {

		pr_err("compressor %s not available, using default %s\n",

		       zswap_compressor, ZSWAP_COMPRESSOR_DEFAULT);

		       zswap_compressor, CONFIG_ZSWAP_COMPRESSOR_DEFAULT);

		param_free_charp(&zswap_compressor);

		zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;

		zswap_compressor = CONFIG_ZSWAP_COMPRESSOR_DEFAULT;

		has_comp = crypto_has_comp(zswap_compressor, 0, 0);

	}

	if (!has_comp) {
@@ -614,11 +613,12 @@ static __init struct zswap_pool *__zswap_pool_create_fallback(void) 
	}



	has_zpool = zpool_has_pool(zswap_zpool_type);

	if (!has_zpool && strcmp(zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT)) {

	if (!has_zpool && strcmp(zswap_zpool_type,

				 CONFIG_ZSWAP_ZPOOL_DEFAULT)) {

		pr_err("zpool %s not available, using default %s\n",

		       zswap_zpool_type, ZSWAP_ZPOOL_DEFAULT);

		       zswap_zpool_type, CONFIG_ZSWAP_ZPOOL_DEFAULT);

		param_free_charp(&zswap_zpool_type);

		zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;

		zswap_zpool_type = CONFIG_ZSWAP_ZPOOL_DEFAULT;

		has_zpool = zpool_has_pool(zswap_zpool_type);

	}

	if (!has_zpool) {