From: Omar Sandoval <osandov@osandov.com>
To: Jens Axboe <axboe@fb.com>
Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH 7/8] wbt: add general throttling mechanism
Date: Thu, 1 Sep 2016 11:05:23 -0700 [thread overview]
Message-ID: <20160901180523.GA3280@vader.DHCP.thefacebook.com> (raw)
In-Reply-To: <1472663151-18560-8-git-send-email-axboe@fb.com>
On Wed, Aug 31, 2016 at 11:05:50AM -0600, Jens Axboe wrote:
> We can hook this up to the block layer, to help throttle buffered
> writes. Or NFS can tap into it, to accomplish the same.
>
> wbt registers a few trace points that can be used to track what is
> happening in the system:
>
> wbt_lat: 259:0: latency 2446318
> wbt_stat: 259:0: rmean=2446318, rmin=2446318, rmax=2446318, rsamples=1,
> wmean=518866, wmin=15522, wmax=5330353, wsamples=57
> wbt_step: 259:0: step down: step=1, window=72727272, background=8, normal=16, max=32
>
> This shows a sync issue event (wbt_lat) that exceeded it's time. wbt_stat
> dumps the current read/write stats for that window, and wbt_step shows a
> step down event where we now scale back writes. Each trace includes the
> device, 259:0 in this case.
>
> Signed-off-by: Jens Axboe <axboe@fb.com>
> ---
> include/linux/wbt.h | 118 +++++++++
> include/trace/events/wbt.h | 122 ++++++++++
> lib/Kconfig | 4 +
> lib/Makefile | 1 +
> lib/wbt.c | 587 +++++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 832 insertions(+)
> create mode 100644 include/linux/wbt.h
> create mode 100644 include/trace/events/wbt.h
> create mode 100644 lib/wbt.c
>
[snip]
> diff --git a/lib/Kconfig b/lib/Kconfig
> index d79909dc01ec..5a65a1f91889 100644
> --- a/lib/Kconfig
> +++ b/lib/Kconfig
> @@ -550,4 +550,8 @@ config STACKDEPOT
> bool
> select STACKTRACE
>
> +config WBT
> + bool
> + select SCALE_BITMAP
Looks like this snuck in from your experiments to get this to work on
top of scale_bitmap?
[snip]
> +void __wbt_done(struct rq_wb *rwb)
> +{
> + int inflight, limit;
> +
> + inflight = atomic_dec_return(&rwb->inflight);
> +
> + /*
> + * wbt got disabled with IO in flight. Wake up any potential
> + * waiters, we don't have to do more than that.
> + */
> + if (unlikely(!rwb_enabled(rwb))) {
> + wake_up_all(&rwb->wait);
> + return;
> + }
> +
> + /*
> + * If the device does write back caching, drop further down
> + * before we wake people up.
> + */
> + if (rwb->wc && !atomic_read(&rwb->bdi->wb.dirty_sleeping))
> + limit = 0;
> + else
> + limit = rwb->wb_normal;
> +
> + /*
> + * Don't wake anyone up if we are above the normal limit.
> + */
> + if (inflight && inflight >= limit)
> + return;
> +
> + if (waitqueue_active(&rwb->wait)) {
> + int diff = limit - inflight;
> +
> + if (!inflight || diff >= rwb->wb_background / 2)
> + wake_up_nr(&rwb->wait, 1);
wake_up(&rwb->wait)?
--
Omar
next prev parent reply other threads:[~2016-09-01 20:57 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-31 17:05 [PATCHSET v6] Throttled background buffered writeback Jens Axboe
2016-08-31 17:05 ` [PATCH 1/8] block: add WRITE_BG Jens Axboe
2016-09-01 7:55 ` Johannes Thumshirn
2016-09-01 7:59 ` Johannes Thumshirn
2016-08-31 17:05 ` [PATCH 2/8] writeback: add wbc_to_write_flags() Jens Axboe
2016-08-31 23:32 ` Omar Sandoval
2016-09-01 3:54 ` Jens Axboe
2016-08-31 17:05 ` [PATCH 3/8] writeback: use WRITE_BG for kupdate and background writeback Jens Axboe
2016-08-31 17:05 ` [PATCH 4/8] writeback: track if we're sleeping on progress in balance_dirty_pages() Jens Axboe
2016-08-31 17:05 ` [PATCH 5/8] block: add code to track actual device queue depth Jens Axboe
2016-08-31 17:05 ` [PATCH 6/8] block: add scalable completion tracking of requests Jens Axboe
2016-08-31 17:05 ` [PATCH 7/8] wbt: add general throttling mechanism Jens Axboe
2016-09-01 18:05 ` Omar Sandoval [this message]
2016-09-01 18:51 ` Jens Axboe
2016-08-31 17:05 ` [PATCH 8/8] writeback: throttle buffered writeback Jens Axboe
-- strict thread matches above, loose matches on Subject: below --
2016-09-07 14:46 [PATCH 0/8] Throttled background buffered writeback v7 Jens Axboe
2016-09-07 14:46 ` [PATCH 7/8] wbt: add general throttling mechanism Jens Axboe
2016-04-26 15:55 [PATCHSET v5] Make background writeback great again for the first time Jens Axboe
2016-04-26 15:55 ` [PATCH 7/8] wbt: add general throttling mechanism Jens Axboe
2016-04-27 12:06 ` xiakaixu
2016-04-27 15:21 ` Jens Axboe
2016-04-28 3:29 ` xiakaixu
2016-04-28 11:05 ` Jan Kara
2016-04-28 18:53 ` Jens Axboe
2016-04-28 19:03 ` Jens Axboe
2016-05-03 9:34 ` Jan Kara
2016-05-03 14:23 ` Jens Axboe
2016-05-03 15:22 ` Jan Kara
2016-05-03 15:32 ` Jens Axboe
2016-05-03 15:40 ` Jan Kara
2016-05-03 15:48 ` Jan Kara
2016-05-03 16:59 ` Jens Axboe
2016-05-03 18:14 ` Jens Axboe
2016-05-03 19:07 ` Jens Axboe
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