Date: Wed, 8 Sep 2021 10:47:37 -0700 From: Colin Percival <cperciva@freebsd.org> To: John Baldwin <jhb@FreeBSD.org>, src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: Re: git: a8b89dff6ac0 - main - Disable acpi_timer_test by default Message-ID: <4b7bf983-8333-f4bc-6ce8-a59ac2fc7380@freebsd.org> In-Reply-To: <f1030cac-a17b-727a-472e-d3d90933da2b@FreeBSD.org> References: <202109080132.1881WXPv069848@gitrepo.freebsd.org> <f1030cac-a17b-727a-472e-d3d90933da2b@FreeBSD.org>
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On 9/8/21 9:01 AM, John Baldwin wrote: > On 9/7/21 6:32 PM, Colin Percival wrote: >> Disable acpi_timer_test by default >> This disables testing the ACPI timer by default, forcing the use of >> ACPI-fast rather than ACPI-safe. The broken-ACPI-timers workaround >> can be re-enabled by setting the hw.acpi.timer_test_enabled=1 tunable. >> This speeds up the FreeBSD boot process by 140 ms on an EC2 c5.xlarge >> instance. >> This change will not be MFCed. >> Assuming no problems are reported, acpi_timer_test, the associated >> tunable, and the ACPI-safe timecounter should be removed in FreeBSD 15. >> Relnotes: The ACPI-safe timer is disabled in favour of >> ACPI-fast; >> if timekeeping issues are observed, please test with >> hw.acpi.timer_test_enabled=1 in loader.conf and report >> if that fixes the problem. > > Perhaps it should default to '1' for i386 and '0' otherwise? The relevant > chipsets were 32-bit only, so this would be a simple way to skip the test for > modern hardware, and you could probably MFC that safely. That option was discussed, but I decided that it was probably safer to keep it enabled by default in 13 in case the test was detecting systems which are broken in other ways. Googling for "ACPI-safe" (which shows up if the test fails) finds forum discussions from the mid-2010s, but it's not clear whether that's due to very old hardware, new ACPI timer issues, or other timekeeping problems -- I figured it was best to play it safe for something which would be going into a stable branch though. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
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