1 From cfe4cda49168a35df7a278e567542c2b7fa096c3 Mon Sep 17 00:00:00 2001
2 From: Phil Elwell <phil@raspberrypi.com>
3 Date: Tue, 5 May 2020 15:23:32 +0100
4 Subject: [PATCH] zswap: Defer zswap initialisation
6 Enabling zswap support in the kernel configuration costs about 1.5MB
7 of RAM, even when zswap is not enabled at runtime. This cost can be
8 reduced significantly by deferring initialisation (including pool
9 creation) until the "enabled" parameter is set to true. There is a
10 small cost to this in that some initialisation code has to remain in
11 memory after the init phase, just in case they are needed later,
12 but the total size increase is negligible.
14 See: https://github.com/raspberrypi/linux/pull/3432
16 Signed-off-by: Phil Elwell <phil@raspberrypi.com>
18 mm/zswap.c | 53 +++++++++++++++++++++++++++++------------------------
19 1 file changed, 29 insertions(+), 24 deletions(-)
23 @@ -663,8 +663,9 @@ error:
27 -static __init struct zswap_pool *__zswap_pool_create_fallback(void)
28 +static bool zswap_try_pool_create(void)
30 + struct zswap_pool *pool;
31 bool has_comp, has_zpool;
33 has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
34 @@ -700,9 +701,21 @@ static __init struct zswap_pool *__zswap
37 if (!has_comp || !has_zpool)
41 + pool = zswap_pool_create(zswap_zpool_type, zswap_compressor);
43 - return zswap_pool_create(zswap_zpool_type, zswap_compressor);
45 + pr_info("loaded using pool %s/%s\n", pool->tfm_name,
46 + zpool_get_type(pool->zpool));
47 + list_add(&pool->list, &zswap_pools);
48 + zswap_has_pool = true;
50 + pr_err("pool creation failed\n");
51 + zswap_enabled = false;
54 + return zswap_enabled;
57 static void zswap_pool_destroy(struct zswap_pool *pool)
58 @@ -875,16 +888,19 @@ static int zswap_zpool_param_set(const c
59 static int zswap_enabled_param_set(const char *val,
60 const struct kernel_param *kp)
64 if (zswap_init_failed) {
65 pr_err("can't enable, initialization failed\n");
68 - if (!zswap_has_pool && zswap_init_started) {
69 - pr_err("can't enable, no pool configured\n");
73 - return param_set_bool(val, kp);
74 + ret = param_set_bool(val, kp);
75 + if (!ret && zswap_enabled && zswap_init_started && !zswap_has_pool)
76 + if (!zswap_try_pool_create())
82 /*********************************
83 @@ -1489,7 +1505,6 @@ static int __init zswap_debugfs_init(voi
84 **********************************/
85 static int __init init_zswap(void)
87 - struct zswap_pool *pool;
90 zswap_init_started = true;
91 @@ -1513,33 +1528,23 @@ static int __init init_zswap(void)
95 - pool = __zswap_pool_create_fallback();
97 - pr_info("loaded using pool %s/%s\n", pool->tfm_name,
98 - zpool_get_type(pool->zpool));
99 - list_add(&pool->list, &zswap_pools);
100 - zswap_has_pool = true;
102 - pr_err("pool creation failed\n");
103 - zswap_enabled = false;
106 shrink_wq = create_workqueue("zswap-shrink");
108 - goto fallback_fail;
111 ret = frontswap_register_ops(&zswap_frontswap_ops);
114 if (zswap_debugfs_init())
115 pr_warn("debugfs initialization failed\n");
118 + zswap_try_pool_create();
123 destroy_workqueue(shrink_wq);
126 - zswap_pool_destroy(pool);
128 cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);