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Date: Tue, 29 Dec 2015 10:19:17 -0700 From: Jens Axboe <axboe@...nel.dk> To: Alexandru Moise <00moses.alexander00@...il.com> Cc: linux-kernel@...r.kernel.org Subject: Re: [PATCH] cfq-iosched: convert slice idle time to jiffies 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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