linux-kernel - Re: [PATCH v2] cfq-iosched: convert group idle time to jiffies

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Date:	Tue, 29 Dec 2015 13:19:57 -0700
From:	Jens Axboe <axboe@...nel.dk>
To:	Alexandru Moise <00moses.alexander00@...il.com>
Cc:	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] cfq-iosched: convert group idle time to jiffies

On 12/29/2015 01:16 PM, Alexandru Moise wrote:
> This patch refers to Jens Axboe's change way back in 2006:
> 7b14e3b52 cfq-iosched: slice expiry fixups
>
> In this patch he fixed a potential timer race condition by delaying
> idle_slice_timer by the slice_idle time value.
>
> Today this timer is delayed by either slice_idle or group_idle time
> values, which on my system, and according to
> Documentation/block/cfq-iosched.txt the default value for group_idle
> is 8ms.
>
> Since the time given by group_idle is supposed to be in milliseconds
> we should convert that value from milliseconds to jiffies before
> adding it to jiffies variable and setting our timer.

Again, the slice idle values are stored in jiffies, there's no need to 
convert. I think you are missing the fact that we display the value in 
msecs, and convert when displaying/storing through sysfs.

-- 
Jens Axboe

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