[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Y0LGLGW7RSlklKyl@hirez.programming.kicks-ass.net>
Date: Sun, 9 Oct 2022 15:01:32 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Feng Tang <feng.tang@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...el.com>,
"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
linux-kernel@...r.kernel.org, rui.zhang@...el.com,
tim.c.chen@...el.com, Xiongfeng Wang <wangxiongfeng2@...wei.com>,
Yu Liao <liaoyu15@...wei.com>
Subject: Re: [PATCH] x86/tsc: Extend the watchdog check exemption to 4S/8S
machine
On Sun, Oct 09, 2022 at 01:12:09PM +0800, Feng Tang wrote:
> There is report again that the tsc clocksource on a 4 sockets x86
> Skylake server was wrongly judged as 'unstable' by 'jiffies' watchdog,
> and disabled [1]. Also we got silimar reports on 8 sockets platform
> from internal test.
>
> Commit b50db7095fe0 ("x86/tsc: Disable clocksource watchdog for TSC
> on qualified platorms") was introduce to deal with these false
> alarms of tsc unstable issues, covering qualified platforms for 2
> sockets or smaller ones.
>
> Extend the exemption also to 4/8 sockets to fix the issue.
>
> Rui also proposed another way to disable 'jiffies' as clocksource
> watchdog [2], which can also solve this specific problem in an
> architecture independent way, with one limitation that some tsc false
> alarms are reported by other watchdogs like HPET in post-boot time,
> while 'jiffies' is mostly used in boot phase before hardware
> clocksources are initialized.
>
> [1]. https://lore.kernel.org/all/9d3bf570-3108-0336-9c52-9bee15767d29@huawei.com/
> [2]. https://lore.kernel.org/all/bd5b97f89ab2887543fc262348d1c7cafcaae536.camel@intel.com/
>
> Reported-by: Yu Liao <liaoyu15@...wei.com>
> Tested-by: Yu Liao <liaoyu15@...wei.com>
> Signed-off-by: Feng Tang <feng.tang@...el.com>
> ---
> arch/x86/kernel/tsc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
> index cafacb2e58cc..b4ea79cb1d1a 100644
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -1217,7 +1217,7 @@ static void __init check_system_tsc_reliable(void)
> if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
> boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
> boot_cpu_has(X86_FEATURE_TSC_ADJUST) &&
> - nr_online_nodes <= 2)
> + nr_online_nodes <= 8)
So you're saying all 8 socket systems since Broadwell (?) are TSC
sync'ed ?
AFAIK there is no architectural guarantee for >4 sockets to have a sane
TSC. If there is one, the above should be limited to architectures that
conform.
Powered by blists - more mailing lists