Date: Thu, 31 Aug 2017 10:21:10 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 221956] cam iosched: Schedule cam_iosched_ticker() quanta times per second Message-ID: <bug-221956-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D221956 Bug ID: 221956 Summary: cam iosched: Schedule cam_iosched_ticker() quanta times per second Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Keywords: patch Severity: Affects Some People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: fk@fabiankeil.de Flags: mfc-stable11? Created attachment 185947 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D185947&action= =3Dedit cam iosched: Schedule cam_iosched_ticker() quanta times per second The attached patch lets 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=3D1000 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 --=20 You are receiving this mail because: You are the assignee for the bug.=
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