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

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Message-ID: <20151229173302.GA13345@gmail.com>
Date:	Tue, 29 Dec 2015 18:33:02 +0100
From:	Alexandru Moise <00moses.alexander00@...il.com>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cfq-iosched: convert slice idle time to jiffies

On Tue, Dec 29, 2015 at 10:19:17AM -0700, Jens Axboe wrote:
> On 12/28/2015 06:08 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 both is 8ms.
> >
> >Since the time given by either variables 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.
> >
> >In my obervations the area is really active as I've seen that function
> >get called a lot for each device on my btrfs raid setup during btrfs
> >check. I've also timed the btrfs check before and after applying the
> >patch and I might've noticed a very slight improvement in execution
> >time but the numbers vary too much for me to post any believable
> >numbers (10 milliseconds difference at most on average).
> 
> cfqd->cfq_slice_idle is in jiffies, it's not in msecs.
> 
> -- 
> Jens Axboe
> 

Then should I only do the conversion in the case of group_idle?
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