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Sender: Tejun Heo <htejun@gmail.com>
Date: Mon, 6 Nov 2017 08:30:40 -0800
From: Tejun Heo <tj@kernel.org>
To: Paolo Valente <paolo.valente@linaro.org>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block <linux-block@vger.kernel.org>,
	Luca Miccio <lucmiccio@gmail.com>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Mark Brown <broonie@kernel.org>, dhowells@redhat.com, hpa@zytor.com,
	akinobu.mita@gmail.com
Subject: Re: high overhead of functions blkg_*stats_* in bfq
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Hello,

On Mon, Nov 06, 2017 at 05:26:38PM +0100, Paolo Valente wrote:
> Yes.  DEBUG_BLK_CGROUP will just serve to keep the for-debugging
> subset switched off even when the dynamic parameter is on.
> 
> We'll wait for possible counter-arguments from Tejun, and then start
> to work on what you propose.

So, I think the only *really* required ones are io_serviced and the
corresponding byte counts, which are tracked by blk-cgroup core
anyway.  Everything else can be hidden behind an obviously debug boot
param, say, bfq.__DEBUG__extra_stats or whatever.

Thanks.

-- 
tejun