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

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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: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vitaly Wool <vitaly.wool@konsulko.com>
Link: http://lkml.kernel.org/r/20200202000112.456103-1-mail@maciej.szmigiero.name
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Maciej S. Szmigiero 2020-04-06 20:08:03 -07:00 committed by Linus Torvalds
parent 4708f31885
commit bb8b93b5b6
3 changed files with 141 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
Documentation/vm/zswap.rst
View File

@ -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.::

118
mm/Kconfig
View File

@ -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

24
mm/zswap.c
View File

@ -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) {