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From: Chris Mason <clm@fb.com>
To: Josef Bacik <josef@toxicpanda.com>
Cc: Nikolay Borisov <nborisov@suse.com>,
	"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH 2/3] btrfs: wakeup cleaner thread when adding delayed iput
Date: Tue, 27 Nov 2018 19:59:42 +0000
Message-ID: <13D3592A-3719-4F9E-8E8A-944FE88F30D4@fb.com> (raw)
In-Reply-To: <20181127195450.fjor2gewhp3hri56@macbook-pro-91.dhcp.thefacebook.com>

On 27 Nov 2018, at 14:54, Josef Bacik wrote:

> On Tue, Nov 27, 2018 at 10:26:15AM +0200, Nikolay Borisov wrote:
>>
>>
>> On 21.11.18 г. 21:09 ч., Josef Bacik wrote:
>>> The cleaner thread usually takes care of delayed iputs, with the
>>> exception of the btrfs_end_transaction_throttle path.  The cleaner
>>> thread only gets woken up every 30 seconds, so instead wake it up to 
>>> do
>>> it's work so that we can free up that space as quickly as possible.
>>
>> Have you done any measurements how this affects the overall system. I
>> suspect this introduces a lot of noise since now we are going to be
>> doing a thread wakeup on every iput, does this give a chance to have
>> nice, large batches of iputs that  the cost of wake up can be 
>> amortized
>> across?
>
> I ran the whole patchset with our A/B testing stuff and the patchset 
> was a 5%
> win overall, so I'm inclined to think it's fine.  Thanks,

It's a good point though, a delayed wakeup may be less overhead.

-chris

  reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-21 19:09 [PATCH 0/3] Delayed iput fixes Josef Bacik
2018-11-21 19:09 ` [PATCH 1/3] btrfs: run delayed iputs before committing Josef Bacik
2018-11-26 14:44   ` Nikolay Borisov
2018-11-21 19:09 ` [PATCH 2/3] btrfs: wakeup cleaner thread when adding delayed iput Josef Bacik
2018-11-27  8:26   ` Nikolay Borisov
2018-11-27 19:54     ` Josef Bacik
2018-11-27 19:59       ` Chris Mason [this message]
2018-11-27 20:08         ` Josef Bacik
2018-11-28 19:06           ` David Sterba
2018-11-28 19:32             ` Chris Mason
2018-11-28 20:08             ` Filipe Manana
2018-11-29  0:30               ` Qu Wenruo
2018-11-21 19:09 ` [PATCH 3/3] btrfs: replace cleaner_delayed_iput_mutex with a waitqueue Josef Bacik
2018-11-27  8:29   ` Nikolay Borisov
2018-11-27 20:01     ` Josef Bacik
2018-12-03 16:06 [PATCH 0/3][V2] Delayed iput fixes Josef Bacik
2018-12-03 16:06 ` [PATCH 2/3] btrfs: wakeup cleaner thread when adding delayed iput Josef Bacik
2018-12-04  9:21   ` Nikolay Borisov
2018-12-04 18:18     ` Josef Bacik
2019-01-11 15:21 [PATCH 0/3][V3] Delayed iput fixes Josef Bacik
2019-01-11 15:21 ` [PATCH 2/3] btrfs: wakeup cleaner thread when adding delayed iput Josef Bacik

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