linux-kernel - Re: [PATCH] nvme: Check for readiness more quickly, to speed up boot time

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Message-ID: <BYAPR04MB574947C1DF24C4DDC04D230786E60@BYAPR04MB5749.namprd04.prod.outlook.com>
Date:   Sun, 1 Mar 2020 19:53:17 +0000
From:   Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>
To:     Keith Busch <kbusch@...nel.org>,
        Josh Triplett <josh@...htriplett.org>
CC:     Jens Axboe <axboe@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH] nvme: Check for readiness more quickly, to speed up boot
 time

Keith,

On 03/01/2020 10:32 AM, Keith Busch wrote:
> The key being this sleep schedules the task unlike udelay. It's neat
> you can boot where 100ms is considered a long time.
>
> This clearly helps when you've one nvme that becomes ready quickly, but
> what happens with many nvme's that are slow to ready? This change will
> end up polling the status of those 1000's of times, I wonder if there's
> a point where this frequent sleep/wake cycle initializing a whole lot
> of nvme devices in parallel may interfere with other init tasks.

This is what I didn't understand, although patch does improves
performance for one controller under one situation, (also after
testing I didn't see big issues with the controllers that I've,
I didn't understand how it will behave with the situation you have
mentioned. But anyways, looks good.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@....com>