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Date: Fri, 22 Oct 2010 20:57:45 +0200 From: Lukas Czerner <lczerner@...hat.com> To: linux-ext4@...r.kernel.org Cc: tytso@....edu, sandeen@...hat.com, lczerner@...hat.com Subject: [PATCH] ext4: fix lazyinit thread prevent from sleep 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@...hat.com> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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