linux-kernel - Re: [PATCH 1/2] regulator: Fix useless O^2 complexity in suspend/resume

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Message-Id: <20180904083901eucas1p17c35261c6dcfd51381dafb3b9b0dfaf7~RJaWxxuug2416824168eucas1p10@eucas1p1.samsung.com>
Date:   Tue, 4 Sep 2018 10:39:00 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Chunyan Zhang <zhang.chunyan@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH 1/2] regulator: Fix useless O^2 complexity in
 suspend/resume

Hi Mark,

On 2018-09-03 17:09, Mark Brown wrote:
> On Mon, Sep 03, 2018 at 04:49:36PM +0200, Marek Szyprowski wrote:
>> regulator_pm_ops with regulator_suspend and regulator_resume functions are
>> assigned to every regulator device registered in the system, so there is no
>> need to iterate over all again in them. Replace class_for_each_device()
>> construction with direct operation on the rdev embedded in the given
>> regulator device. This saves a lots of useless operations in suspend and
>> resume paths.
> This would've been better as the second patch since it's an optimization
> and not so urgent for stable.

Frankly, the slow down caused by this O^2 in case of 40 regulators in the
system (not that unusual in nowadays mobiles) is noticeable and quite
annoying. IMHO this is still a good candidate for stable.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland