In my test lazyinit threat (in linux-next tree) consumes too much CPU
(90%). The reason is that there is a bug preventing the threat to sleep
and hence it keeps walking the li_request_list until the time for next
scheduled request comes.
It is because the next_wakeup is originally set to jiffies - 1 so the
thread is assuming that there is no reason to sleep, because the time
for next scheduled event is already came, however that is not true.
I have fixed that by setting next_wakeup to MAX_JIFFY_OFFSET initially
and than setting value of the next scheduled request (the one with the
smallest lr_next_sched value). It has been tested and now the CPU
utilization of lazyinit thread is under 1% (with one request in the list).
Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
---
fs/ext4/super.c | 9 +++++----
1 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 82ceb8b..f0b424a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2710,7 +2710,7 @@ static int ext4_lazyinit_thread(void *arg)
cont_thread:
while (true) {
- next_wakeup = jiffies-1;
+ next_wakeup = MAX_JIFFY_OFFSET;
mutex_lock(&eli->li_list_mtx);
if (list_empty(&eli->li_request_list)) {
@@ -2722,10 +2722,11 @@ cont_thread:
elr = list_entry(pos, struct ext4_li_request,
lr_request);
- if (time_before_eq(jiffies, elr->lr_next_sched))
- continue;
+ if (time_after_eq(jiffies, elr->lr_next_sched))
+ ret = ext4_run_li_request(elr);
- if ((ret = ext4_run_li_request(elr)) != 0) {
+ if (ret) {
+ ret = 0;
ext4_remove_li_request(elr);
continue;
}
--
1.7.2.3
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