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Date: Thu, 6 Aug 2015 09:08:43 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To: Dan Streetman <ddstreet@...e.org>
Cc: Seth Jennings <sjennings@...iantweb.net>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] zswap: change zpool/compressor at runtime
Hi,
On (08/05/15 09:46), Dan Streetman wrote:
> Update the zpool and compressor parameters to be changeable at runtime.
> When changed, a new pool is created with the requested zpool/compressor,
> and added as the current pool at the front of the pool list. Previous
> pools remain in the list only to remove existing compressed pages from.
> The old pool(s) are removed once they become empty.
>
Sorry, just curious, is this functionality/complication really
necessary? How often do you expect people to do that? The way I
see it -- a static configuration works just fine: boot, test,
re-configure, boot test; compare the results and done.
-ss
> Signed-off-by: Dan Streetman <ddstreet@...e.org>
> ---
> mm/zswap.c | 135 +++++++++++++++++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 122 insertions(+), 13 deletions(-)
>
> diff --git a/mm/zswap.c b/mm/zswap.c
> index f8fcd7e..3eaff21 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -80,23 +80,39 @@ static u64 zswap_duplicate_entry;
> static bool zswap_enabled;
> module_param_named(enabled, zswap_enabled, bool, 0644);
>
> -/* Compressor to be used by zswap (fixed at boot for now) */
> +/* Crypto compressor to use */
> #define ZSWAP_COMPRESSOR_DEFAULT "lzo"
> -static char *zswap_compressor = ZSWAP_COMPRESSOR_DEFAULT;
> -module_param_named(compressor, zswap_compressor, charp, 0444);
> -
> -/* The maximum percentage of memory that the compressed pool can occupy */
> -static unsigned int zswap_max_pool_percent = 20;
> -module_param_named(max_pool_percent,
> - zswap_max_pool_percent, uint, 0644);
> +static char zswap_compressor[CRYPTO_MAX_ALG_NAME] = ZSWAP_COMPRESSOR_DEFAULT;
> +static struct kparam_string zswap_compressor_kparam = {
> + .string = zswap_compressor,
> + .maxlen = sizeof(zswap_compressor),
> +};
> +static int zswap_compressor_param_set(const char *,
> + const struct kernel_param *);
> +static struct kernel_param_ops zswap_compressor_param_ops = {
> + .set = zswap_compressor_param_set,
> + .get = param_get_string,
> +};
> +module_param_cb(compressor, &zswap_compressor_param_ops,
> + &zswap_compressor_kparam, 0644);
>
> -/* Compressed storage to use */
> +/* Compressed storage zpool to use */
> #define ZSWAP_ZPOOL_DEFAULT "zbud"
> -static char *zswap_zpool_type = ZSWAP_ZPOOL_DEFAULT;
> -module_param_named(zpool, zswap_zpool_type, charp, 0444);
> +static char zswap_zpool_type[32 /* arbitrary */] = ZSWAP_ZPOOL_DEFAULT;
> +static struct kparam_string zswap_zpool_kparam = {
> + .string = zswap_zpool_type,
> + .maxlen = sizeof(zswap_zpool_type),
> +};
> +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,
> + .get = param_get_string,
> +};
> +module_param_cb(zpool, &zswap_zpool_param_ops, &zswap_zpool_kparam, 0644);
>
> -/* zpool is shared by all of zswap backend */
> -static struct zpool *zswap_pool;
> +/* The maximum percentage of memory that the compressed pool can occupy */
> +static unsigned int zswap_max_pool_percent = 20;
> +module_param_named(max_pool_percent, zswap_max_pool_percent, uint, 0644);
>
> /*********************************
> * data structures
> @@ -161,6 +177,9 @@ static LIST_HEAD(zswap_pools);
> /* protects zswap_pools list modification */
> static DEFINE_SPINLOCK(zswap_pools_lock);
>
> +/* used by param callback function */
> +static bool zswap_init_started;
> +
> /*********************************
> * helpers and fwd declarations
> **********************************/
> @@ -661,6 +680,94 @@ static void zswap_pool_put(struct zswap_pool *pool)
> kref_put(&pool->kref, __zswap_pool_empty);
> }
>
> +/*********************************
> +* param callbacks
> +**********************************/
> +
> +static int __zswap_param_set(const char *val, const struct kernel_param *kp,
> + char *type, char *compressor)
> +{
> + struct zswap_pool *pool, *put_pool = NULL;
> + char str[kp->str->maxlen], *s;
> + int ret;
> +
> + strlcpy(str, val, kp->str->maxlen);
> + s = strim(str);
> +
> + /* if this is load-time (pre-init) param setting,
> + * don't create a pool; that's done during init.
> + */
> + if (!zswap_init_started)
> + return param_set_copystring(s, kp);
> +
> + /* no change required */
> + if (!strncmp(kp->str->string, s, kp->str->maxlen))
> + return 0;
> +
> + if (!type) {
> + type = s;
> + if (!zpool_has_pool(type)) {
> + pr_err("zpool %s not available\n", type);
> + return -ENOENT;
> + }
> + } else if (!compressor) {
> + compressor = s;
> + if (!crypto_has_comp(compressor, 0, 0)) {
> + pr_err("compressor %s not available\n", compressor);
> + return -ENOENT;
> + }
> + }
> +
> + spin_lock(&zswap_pools_lock);
> +
> + pool = zswap_pool_find_get(type, compressor);
> + if (pool) {
> + zswap_pool_debug("using existing", pool);
> + list_del_rcu(&pool->list);
> + } else {
> + spin_unlock(&zswap_pools_lock);
> + pool = zswap_pool_create(type, compressor);
> + spin_lock(&zswap_pools_lock);
> + }
> +
> + if (pool)
> + ret = param_set_copystring(s, kp);
> + else
> + ret = -EINVAL;
> +
> + if (!ret) {
> + put_pool = zswap_pool_current();
> + list_add_rcu(&pool->list, &zswap_pools);
> + } else if (pool) {
> + /* add the possibly pre-existing pool to the end of the pools
> + * list; if it's new (and empty) then it'll be removed and
> + * destroyed by the put after we drop the lock
> + */
> + list_add_tail_rcu(&pool->list, &zswap_pools);
> + put_pool = pool;
> + }
> +
> + spin_unlock(&zswap_pools_lock);
> +
> + /* drop the ref from either the old current pool,
> + * or the new pool we failed to add
> + */
> + if (put_pool)
> + zswap_pool_put(put_pool);
> +
> + return ret;
> +}
> +
> +static int zswap_compressor_param_set(const char *val,
> + const struct kernel_param *kp)
> +{
> + return __zswap_param_set(val, kp, zswap_zpool_type, NULL);
> +}
> +
> +static int zswap_zpool_param_set(const char *val,
> + const struct kernel_param *kp)
> +{
> + return __zswap_param_set(val, kp, NULL, zswap_compressor);
> }
>
> /*********************************
> @@ -1116,6 +1223,8 @@ static int __init init_zswap(void)
> {
> struct zswap_pool *pool;
>
> + zswap_init_started = true;
> +
> if (zswap_entry_cache_create()) {
> pr_err("entry cache creation failed\n");
> goto cache_fail;
> --
> 2.1.0
>
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