Attachment 185971 Details for Bug 221974 – cam iosched: Enforce iop limits below the quanta value and preserve "unspent" ios

[patch] cam iosched: Enforce iop limits below the quanta value and preserve "unspent" ios

cam-iosched-Enforce-iop-limits-below-the-quanta-value-and-preserve-unspent-ios.diff (text/plain), 3.09 KB, created by Fabian Keil on 2017-09-01 10:30:19 UTC

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Creator: Fabian Keil

Created: 2017-09-01 10:30:19 UTC

Size: 3.09 KB

patch

obsolete

>From 1e67040c6960d2f503f7da082727d64bfd55a83a Mon Sep 17 00:00:00 2001
>From: Fabian Keil <fk@fabiankeil.de>
>Date: Wed, 2 Aug 2017 13:16:01 +0200
>Subject: [PATCH 7/8] cam iosched: Enforce iop limits below the quanta value
>
>Previously the iops limiter would always allow at least
>quanta ios per second as cam_iosched_iops_tick() never set
>ios->l_value1 below 1.
>
>Obtained from: ElectroBSD
>---
> sys/cam/cam_iosched.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
>diff --git a/sys/cam/cam_iosched.c b/sys/cam/cam_iosched.c
>index 77ad53269cd2..2ebe4538a4e1 100644
>--- a/sys/cam/cam_iosched.c
>+++ b/sys/cam/cam_iosched.c
>@@ -415,6 +415,7 @@ cam_iosched_iops_init(struct iop_stats *ios)
> 	ios->l_value1 = ios->current / ios->softc->quanta;
> 	if (ios->l_value1 <= 0)
> 		ios->l_value1 = 1;
>+	ios->l_value2 = 0;
> 
> 	return 0;
> }
>@@ -423,9 +424,18 @@ static int
> cam_iosched_iops_tick(struct iop_stats *ios)
> {
> 
>+	if ((ios->softc->total_ticks % ios->softc->quanta) == 0)
>+		ios->l_value2 = 0;
>+
> 	ios->l_value1 = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16);
>-	if (ios->l_value1 <= 0)
>+	/*
>+	 * Allow at least one IO per tick until all
>+	 * the IOs for this interval have been spent.
>+	 */
>+	if (ios->l_value1 <= 0 && ios->l_value2 < ios->current) {
> 		ios->l_value1 = 1;
>+		ios->l_value2++;
>+	}
> 
> 	return 0;
> }
>-- 
>2.14.1
>
>From 90848077590580bf1d2ec0a61add4818bb657876 Mon Sep 17 00:00:00 2001
>From: Fabian Keil <fk@fabiankeil.de>
>Date: Wed, 2 Aug 2017 15:38:10 +0200
>Subject: [PATCH 8/8] cam iosched: Prevent cam_iosched_iops_tick() from
> discarding 'unspent' ios
>
>... unless it's a new accounting interval.
>
>Previously ios that weren't used between ticks were lost,
>as a result the iops limiter could enforce a limit below the
>configured maximum.
>
>Obtained from: ElectroBSD
>---
> sys/cam/cam_iosched.c | 22 ++++++++++++++++------
> 1 file changed, 16 insertions(+), 6 deletions(-)
>
>diff --git a/sys/cam/cam_iosched.c b/sys/cam/cam_iosched.c
>index 2ebe4538a4e1..cee93c9712a0 100644
>--- a/sys/cam/cam_iosched.c
>+++ b/sys/cam/cam_iosched.c
>@@ -423,20 +423,30 @@ cam_iosched_iops_init(struct iop_stats *ios)
> static int
> cam_iosched_iops_tick(struct iop_stats *ios)
> {
>+	int new_ios;
> 
>-	if ((ios->softc->total_ticks % ios->softc->quanta) == 0)
>-		ios->l_value2 = 0;
>-
>-	ios->l_value1 = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16);
>+	new_ios = (int)((ios->current * (uint64_t)ios->softc->this_frac) >> 16);
> 	/*
> 	 * Allow at least one IO per tick until all
> 	 * the IOs for this interval have been spent.
> 	 */
>-	if (ios->l_value1 <= 0 && ios->l_value2 < ios->current) {
>-		ios->l_value1 = 1;
>+	if (new_ios < 1 && ios->l_value2 < ios->current) {
>+		new_ios = 1;
> 		ios->l_value2++;
> 	}
> 
>+        /*
>+         * If this a new accounting interval, discard any "unspent" ios
>+         * granted in the previous interval.  Otherwise add the new ios to
>+         * the previously granted ones that haven't been spent yet.
>+         */
>+	if ((ios->softc->total_ticks % ios->softc->quanta) == 0) {
>+		ios->l_value1 = new_ios;
>+		ios->l_value2 = 1;
>+	} else {
>+		ios->l_value1 += new_ios;
>+	}
>+
> 	return 0;
> }
> 
>-- 
>2.14.1
>

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Attachments on bug 221974: 185971