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Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending !nr_pages flush

From Jens Axboe <axboe@kernel.dk>
Newsgroups linux.kernel
Subject Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending !nr_pages flush
Date 2017-09-20 04:00 +0200
Message-ID <urCsV-4FV-7@gated-at.bofh.it> (permalink)
References <urwQx-1e6-3@gated-at.bofh.it> <urwQz-1e6-39@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 09/19/2017 01:53 PM, Jens Axboe wrote:
> @@ -948,15 +949,25 @@ static void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
>  			       bool range_cyclic, enum wb_reason reason)
>  {
>  	struct wb_writeback_work *work;
> +	bool zero_pages = false;
>  
>  	if (!wb_has_dirty_io(wb))
>  		return;
>  
>  	/*
> -	 * If someone asked for zero pages, we write out the WORLD
> +	 * If someone asked for zero pages, we write out the WORLD.
> +	 * Places like vmscan and laptop mode want to queue a wakeup to
> +	 * the flusher threads to clean out everything. To avoid potentially
> +	 * having tons of these pending, ensure that we only allow one of
> +	 * them pending and inflight at the time
>  	 */
> -	if (!nr_pages)
> +	if (!nr_pages) {
> +		if (test_bit(WB_zero_pages, &wb->state))
> +			return;
> +		set_bit(WB_zero_pages, &wb->state);
>  		nr_pages = get_nr_dirty_pages();
> +		zero_pages = true;
> +	}

Later fix added here to ensure we clear WB_zero_pages, if work
allocation fails:

work = kzalloc(sizeof(*work),                                           
                GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN);           
if (!work) {                                                            
        if (zero_pages)                                                 
                clear_bit(WB_zero_pages, &wb->state);
	[...]

Updated patch here:

http://git.kernel.dk/cgit/linux-block/commit/?h=writeback-fixup&id=21ea70657894fda9fccf257543cbec112b2813ef

-- 
Jens Axboe

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Thread

[PATCH 0/6] More graceful flusher thread memory reclaim wakeup Jens Axboe <axboe@kernel.dk> - 2017-09-19 22:00 +0200
  [PATCH 3/6] page-writeback: pass in '0' for nr_pages writeback in laptop mode Jens Axboe <axboe@kernel.dk> - 2017-09-19 22:00 +0200
    Re: [PATCH 3/6] page-writeback: pass in '0' for nr_pages writeback  in laptop mode Johannes Weiner <hannes@cmpxchg.org> - 2017-09-19 22:10 +0200
    Re: [PATCH 3/6] page-writeback: pass in '0' for nr_pages writeback  in laptop mode Jan Kara <jack@suse.cz> - 2017-09-20 16:40 +0200
      Re: [PATCH 3/6] page-writeback: pass in '0' for nr_pages writeback in  laptop mode Jens Axboe <axboe@kernel.dk> - 2017-09-20 17:30 +0200
  [PATCH 2/6] fs-writeback: provide a wakeup_flusher_threads_bdi() Jens Axboe <axboe@kernel.dk> - 2017-09-19 22:00 +0200
    Re: [PATCH 2/6] fs-writeback: provide a wakeup_flusher_threads_bdi() Johannes Weiner <hannes@cmpxchg.org> - 2017-09-19 22:10 +0200
    Re: [PATCH 2/6] fs-writeback: provide a wakeup_flusher_threads_bdi() Jan Kara <jack@suse.cz> - 2017-09-20 16:30 +0200
  [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one location Jens Axboe <axboe@kernel.dk> - 2017-09-19 22:00 +0200
    Re: [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one  location Johannes Weiner <hannes@cmpxchg.org> - 2017-09-19 22:10 +0200
    Re: [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one  location Jan Kara <jack@suse.cz> - 2017-09-20 16:50 +0200
      Re: [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one  location Jens Axboe <axboe@kernel.dk> - 2017-09-20 17:10 +0200
        Re: [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one  location Jan Kara <jack@suse.cz> - 2017-09-20 17:40 +0200
          Re: [PATCH 5/6] fs-writeback: move nr_pages == 0 logic to one  location Jens Axboe <axboe@kernel.dk> - 2017-09-20 17:50 +0200
  [PATCH 1/6] buffer: cleanup free_more_memory() flusher wakeup Jens Axboe <axboe@kernel.dk> - 2017-09-19 22:00 +0200
    Re: [PATCH 1/6] buffer: cleanup free_more_memory() flusher wakeup Johannes Weiner <hannes@cmpxchg.org> - 2017-09-19 22:10 +0200
    Re: [PATCH 1/6] buffer: cleanup free_more_memory() flusher wakeup Jan Kara <jack@suse.cz> - 2017-09-20 16:20 +0200
      Re: [PATCH 1/6] buffer: cleanup free_more_memory() flusher wakeup Jens Axboe <axboe@kernel.dk> - 2017-09-20 17:20 +0200
  [PATCH 6/6] fs-writeback: only allow one inflight and pending !nr_pages flush Jens Axboe <axboe@kernel.dk> - 2017-09-19 22:00 +0200
    Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending  !nr_pages flush Johannes Weiner <hannes@cmpxchg.org> - 2017-09-19 22:20 +0200
      Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending  !nr_pages flush Jens Axboe <axboe@kernel.dk> - 2017-09-19 22:40 +0200
    Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending  !nr_pages flush Jens Axboe <axboe@kernel.dk> - 2017-09-20 04:00 +0200
    Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending  !nr_pages flush Amir Goldstein <amir73il@gmail.com> - 2017-09-20 05:20 +0200
      Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending  !nr_pages flush Jens Axboe <axboe@kernel.dk> - 2017-09-20 06:20 +0200
        Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending  !nr_pages flush Amir Goldstein <amir73il@gmail.com> - 2017-09-20 08:10 +0200
          Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending  !nr_pages flush Jens Axboe <axboe@kernel.dk> - 2017-09-20 14:40 +0200
        Re: [PATCH 6/6] fs-writeback: only allow one inflight and pending  !nr_pages flush Jan Kara <jack@suse.cz> - 2017-09-20 16:50 +0200
  Re: [PATCH 0/6] More graceful flusher thread memory reclaim wakeup John Stoffel <john@quad.stoffel.home> - 2017-09-20 21:40 +0200
    Re: [PATCH 0/6] More graceful flusher thread memory reclaim wakeup Jens Axboe <axboe@kernel.dk> - 2017-09-20 21:40 +0200
      Re: [PATCH 0/6] More graceful flusher thread memory reclaim wakeup Johannes Weiner <hannes@cmpxchg.org> - 2017-09-21 01:20 +0200

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