Attachment 185947 Details for Bug 221956 – cam iosched: Schedule cam_iosched_ticker() quanta times per second

[patch] cam iosched: Schedule cam_iosched_ticker() quanta times per second

0004-cam-iosched-Schedule-cam_iosched_ticker-quanta-times-.diff (text/plain), 2.24 KB, created by Fabian Keil on 2017-08-31 10:21:10 UTC

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Creator: Fabian Keil

Created: 2017-08-31 10:21:10 UTC

Size: 2.24 KB

patch

obsolete

>From eb82a8f272edcdaf4ef2c15b7a9b8fcff920c657 Mon Sep 17 00:00:00 2001
>From: Fabian Keil <fk@fabiankeil.de>
>Date: Thu, 3 Aug 2017 11:54:24 +0200
>Subject: [PATCH 4/8] cam iosched: Schedule cam_iosched_ticker() quanta times
> per second
>
>According to callout_reset(9), "[w]hen ticks is used, the callout is
>scheduled to execute after ticks/hz seconds".
>
>It follows that to get quanta calls per second one should specify
>a tick value of hz / isc->quanta.
>
>Previously the value was additionally reduced by one.
>
>As a result cam_iosched_ticker() was called more often than
>requested by the user and expected by some of the limiters.
>
>On a system with hz=1000 a quanta value of 200 resulted in 250
>calls and a value of 100 in 111 calls.
>
>Without the unexplained tick reduction the number of calls matches
>the quanta value reasonably well.
>
>Obtained from: ElectroBSD
>---
> sys/cam/cam_iosched.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
>diff --git a/sys/cam/cam_iosched.c b/sys/cam/cam_iosched.c
>index 8d39c32511c8..f2e69d9fd84c 100644
>--- a/sys/cam/cam_iosched.c
>+++ b/sys/cam/cam_iosched.c
>@@ -533,7 +533,7 @@ cam_iosched_ticker(void *arg)
> 	sbintime_t now, delta;
> 	int pending;
> 
>-	callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc);
>+	callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc);
> 
> 	now = sbinuptime();
> 	delta = now - isc->last_time;
>@@ -795,7 +795,7 @@ cam_iosched_limiter_sysctl(SYSCTL_HANDLER_ARGS)
> 			return error;
> 		}
> 		/* Note: disk load averate requires ticker to be always running */
>-		callout_reset(&isc->ticker, hz / isc->quanta - 1, cam_iosched_ticker, isc);
>+		callout_reset(&isc->ticker, hz / isc->quanta, cam_iosched_ticker, isc);
> 		isc->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
> 
> 		cam_periph_unlock(isc->periph);
>@@ -1031,7 +1031,7 @@ cam_iosched_init(struct cam_iosched_softc **iscp, struct cam_periph *periph)
> 		callout_init_mtx(&(*iscp)->ticker, cam_periph_mtx(periph), 0);
> 		(*iscp)->periph = periph;
> 		cam_iosched_cl_init(&(*iscp)->cl, *iscp);
>-		callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta - 1, cam_iosched_ticker, *iscp);
>+		callout_reset(&(*iscp)->ticker, hz / (*iscp)->quanta, cam_iosched_ticker, *iscp);
> 		(*iscp)->flags |= CAM_IOSCHED_FLAG_CALLOUT_ACTIVE;
> 	}
> #endif
>-- 
>2.14.1
>

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Attachments on bug 221956: 185947