target/linux/bcm27xx/patches-6.1/950-0238-zswap-Defer-zswap-initialisation.patch

   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
   5
   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.
  13
  14 See: https://github.com/raspberrypi/linux/pull/3432
  15
  16 Signed-off-by: Phil Elwell <phil@raspberrypi.com>
  17 ---
  18  mm/zswap.c | 53 +++++++++++++++++++++++++++++------------------------
  19  1 file changed, 29 insertions(+), 24 deletions(-)
  20
  21 --- a/mm/zswap.c
  22 +++ b/mm/zswap.c
  23 @@ -663,8 +663,9 @@ error:
  24         return NULL;
  25  }
  26
  27 -static __init struct zswap_pool *__zswap_pool_create_fallback(void)
  28 +static bool zswap_try_pool_create(void)
  29  {
  30 +       struct zswap_pool *pool;
  31         bool has_comp, has_zpool;
  32
  33         has_comp = crypto_has_acomp(zswap_compressor, 0, 0);
  34 @@ -700,9 +701,21 @@ static __init struct zswap_pool *__zswap
  35         }
  36
  37         if (!has_comp || !has_zpool)
  38 -               return NULL;
  39 +               return false;
  40 +
  41 +       pool = zswap_pool_create(zswap_zpool_type, zswap_compressor);
  42
  43 -       return zswap_pool_create(zswap_zpool_type, zswap_compressor);
  44 +       if (pool) {
  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;
  49 +       } else {
  50 +               pr_err("pool creation failed\n");
  51 +               zswap_enabled = false;
  52 +       }
  53 +
  54 +       return zswap_enabled;
  55  }
  56
  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)
  61  {
  62 +       int ret;
  63 +
  64         if (zswap_init_failed) {
  65                 pr_err("can't enable, initialization failed\n");
  66                 return -ENODEV;
  67         }
  68 -       if (!zswap_has_pool && zswap_init_started) {
  69 -               pr_err("can't enable, no pool configured\n");
  70 -               return -ENODEV;
  71 -       }
  72
  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())
  77 +                       ret = -ENODEV;
  78 +
  79 +       return ret;
  80  }
  81
  82  /*********************************
  83 @@ -1489,7 +1505,6 @@ static int __init zswap_debugfs_init(voi
  84  **********************************/
  85  static int __init init_zswap(void)
  86  {
  87 -       struct zswap_pool *pool;
  88         int ret;
  89
  90         zswap_init_started = true;
  91 @@ -1513,33 +1528,23 @@ static int __init init_zswap(void)
  92         if (ret)
  93                 goto hp_fail;
  94
  95 -       pool = __zswap_pool_create_fallback();
  96 -       if (pool) {
  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;
 101 -       } else {
 102 -               pr_err("pool creation failed\n");
 103 -               zswap_enabled = false;
 104 -       }
 105 -
 106         shrink_wq = create_workqueue("zswap-shrink");
 107         if (!shrink_wq)
 108 -               goto fallback_fail;
 109 +               goto hp_fail;
 110
 111         ret = frontswap_register_ops(&zswap_frontswap_ops);
 112         if (ret)
 113                 goto destroy_wq;
 114         if (zswap_debugfs_init())
 115                 pr_warn("debugfs initialization failed\n");
 116 +
 117 +       if (zswap_enabled)
 118 +               zswap_try_pool_create();
 119 +
 120         return 0;
 121
 122  destroy_wq:
 123         destroy_workqueue(shrink_wq);
 124 -fallback_fail:
 125 -       if (pool)
 126 -               zswap_pool_destroy(pool);
 127  hp_fail:
 128         cpuhp_remove_state(CPUHP_MM_ZSWP_MEM_PREPARE);
 129  dstmem_fail: