From: Jan Kara <jack@suse.cz>
To: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, hannes@cmpxchg.org, clm@fb.com, jack@suse.cz
Subject: Re: [PATCH 7/7] fs-writeback: only allow one inflight and pending full flush
Date: Mon, 25 Sep 2017 11:35:32 +0200 [thread overview]
Message-ID: <20170925093532.GC5741@quack2.suse.cz> (raw)
In-Reply-To: <3682c4c2-6e8a-e883-9f62-455ea2944496@kernel.dk>
On Thu 21-09-17 10:00:25, Jens Axboe wrote:
> On 09/21/2017 09:36 AM, Jens Axboe wrote:
> >> But more importantly once we are not guaranteed that we only have
> >> a single global wb_writeback_work per bdi_writeback we should just
> >> embedd that into struct bdi_writeback instead of dynamically
> >> allocating it.
> >
> > We could do this as a followup. But right now the logic is that we
> > can have on started (inflight), and still have one new queued.
>
> Something like the below would fit on top to do that. Gets rid of the
> allocation and embeds the work item for global start-all in the
> bdi_writeback structure.
Hum, so when we consider stuff like embedded work item, I would somewhat
prefer to handle this like we do for for_background and for_kupdate style
writeback so that we don't have another special case. For these don't queue
any item, we just queue writeback work into the workqueue (via
wb_wakeup()). When flusher work gets processed wb_do_writeback() checks
(after processing all normal writeback requests) whether conditions for
these special writeback styles are met and if yes, it creates on-stack work
item and processes it (see wb_check_old_data_flush() and
wb_check_background_flush()).
So in this case we would just set some flag in bdi_writeback when memory
reclaim needs help and wb_do_writeback() would check for this flag and
create and process writeback-all style writeback work. Granted this does
not preserve ordering of requests (basically any specific request gets
priority over writeback-whole-world request) but memory gets cleaned in
either case so flusher should be doing what is needed.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
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next prev parent reply other threads:[~2017-09-25 9:35 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-20 15:32 [PATCH 0/7 v2] More graceful flusher thread memory reclaim wakeup Jens Axboe
2017-09-20 15:32 ` [PATCH 1/7] buffer: cleanup free_more_memory() flusher wakeup Jens Axboe
2017-09-21 14:55 ` Christoph Hellwig
2017-09-20 15:32 ` [PATCH 2/7] fs: kill 'nr_pages' argument from wakeup_flusher_threads() Jens Axboe
2017-09-21 14:55 ` Christoph Hellwig
2017-09-22 13:12 ` Jan Kara
2017-09-20 15:32 ` [PATCH 3/7] fs-writeback: provide a wakeup_flusher_threads_bdi() Jens Axboe
2017-09-21 14:56 ` Christoph Hellwig
2017-09-20 15:32 ` [PATCH 4/7] page-writeback: pass in '0' for nr_pages writeback in laptop mode Jens Axboe
2017-09-21 14:59 ` Christoph Hellwig
2017-09-25 14:57 ` Jens Axboe
2017-09-21 15:00 ` Christoph Hellwig
2017-09-22 13:14 ` Jan Kara
2017-09-20 15:33 ` [PATCH 5/7] fs-writeback: make wb_start_writeback() static Jens Axboe
2017-09-21 15:01 ` Christoph Hellwig
2017-09-20 15:33 ` [PATCH 6/7] fs-writeback: move nr_pages == 0 logic to one location Jens Axboe
2017-09-21 15:02 ` Christoph Hellwig
2017-09-22 13:17 ` Jan Kara
2017-09-20 15:33 ` [PATCH 7/7] fs-writeback: only allow one inflight and pending full flush Jens Axboe
2017-09-21 15:05 ` Christoph Hellwig
2017-09-21 15:36 ` Jens Axboe
2017-09-21 16:00 ` Jens Axboe
2017-09-21 17:33 ` Christoph Hellwig
2017-09-25 9:35 ` Jan Kara [this message]
2017-09-25 14:48 ` Jens Axboe
2017-09-28 18:09 ` Jens Axboe
2017-09-29 23:20 ` Jens Axboe
2017-10-02 14:53 ` Jan Kara
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