f2fs: fix the periodic wakeups of discard thread

Fix the unnecessary periodic wakeups of discard thread that happens under
below two conditions -

1. When f2fs is heavily utilized over 80%, the current discard policy
sets the max sleep timeout of discard thread as 50ms
(DEF_MIN_DISCARD_ISSUE_TIME). But this is set even when there are
no pending discard commands to be issued.

2. In the issue_discard_thread() path when there are no pending discard
commands, it fails to reset the wait_ms to max timeout value.

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 44897cf..5bd0e1d 100644 (file)
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1114,6 +1114,8 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
                                struct discard_policy *dpolicy,
                                int discard_type, unsigned int granularity)
 {
+       struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
+
        /* common policy */
        dpolicy->type = discard_type;
        dpolicy->sync = true;
@@ -1133,7 +1135,9 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
                dpolicy->ordered = true;
                if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL) {
                        dpolicy->granularity = 1;
-                       dpolicy->max_interval = DEF_MIN_DISCARD_ISSUE_TIME;
+                       if (atomic_read(&dcc->discard_cmd_cnt))
+                               dpolicy->max_interval =
+                                       DEF_MIN_DISCARD_ISSUE_TIME;
                }
        } else if (discard_type == DPOLICY_FORCE) {
                dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME;
@@ -1749,8 +1753,15 @@ static int issue_discard_thread(void *data)
        set_freezable();
 
        do {
-               __init_discard_policy(sbi, &dpolicy, DPOLICY_BG,
-                                       dcc->discard_granularity);
+               if (sbi->gc_mode == GC_URGENT_HIGH ||
+                       !f2fs_available_free_memory(sbi, DISCARD_CACHE))
+                       __init_discard_policy(sbi, &dpolicy, DPOLICY_FORCE, 1);
+               else
+                       __init_discard_policy(sbi, &dpolicy, DPOLICY_BG,
+                                               dcc->discard_granularity);
+
+               if (!atomic_read(&dcc->discard_cmd_cnt))
+                      wait_ms = dpolicy.max_interval;
 
                wait_event_interruptible_timeout(*q,
                                kthread_should_stop() || freezing(current) ||
@@ -1777,10 +1788,6 @@ static int issue_discard_thread(void *data)
                if (!atomic_read(&dcc->discard_cmd_cnt))
                        continue;
 
-               if (sbi->gc_mode == GC_URGENT_HIGH ||
-                       !f2fs_available_free_memory(sbi, DISCARD_CACHE))
-                       __init_discard_policy(sbi, &dpolicy, DPOLICY_FORCE, 1);
-
                sb_start_intwrite(sbi->sb);
 
                issued = __issue_discard_cmd(sbi, &dpolicy);