Date: Fri, 20 Apr 2018 00:45:50 +0300 From: Konstantin Belousov <kib@freebsd.org> To: Conrad Meyer <cem@freebsd.org> Cc: Colin Percival <cperciva@tarsnap.com>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: RFC: Hiding per-CPU kernel output behind bootverbose Message-ID: <20180419214550.GF6887@kib.kiev.ua> In-Reply-To: <CAG6CVpUerOo%2B55nJq61Hy83RYpbOZS6puEDuemspfNS12urZZw@mail.gmail.com> References: <01000162df15f856-1e5d2641-2a72-4250-8d8e-adcd47bc5db4-000000@email.amazonses.com> <20180419204405.GE6887@kib.kiev.ua> <CAG6CVpUerOo%2B55nJq61Hy83RYpbOZS6puEDuemspfNS12urZZw@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, Apr 19, 2018 at 02:37:56PM -0700, Conrad Meyer wrote: > On Thu, Apr 19, 2018 at 1:44 PM, Konstantin Belousov > <kostikbel@gmail.com> wrote: > > On Thu, Apr 19, 2018 at 06:06:21PM +0000, Colin Percival wrote: > >> On large systems (e.g., EC2's x1e.32xlarge instance type, with 128 vCPUs) > >> the boot time console output contains a large number of lines of the forms > >> > >> SMP: AP CPU #N Launched! > >> cpuN: <ACPI CPU> on acpi0 > >> estN: <Enhanced SpeedStep Frequency Control> on cpuN > >> > >> Having 128 almost-identical lines of output doesn't seem very useful, and > >> it actually has a nontrivial impact on the time spent booting. > >> > >> Does anyone mind if I hide these by default, having them only show up if > >> boot verbosity is requested? > > +1. For the device attaches, perhaps it makes sense to add a device > 'spammy' flag, and set it for per-CPU devices like cpuN or estN. Then > the generic attach code can choose whether to print spammy attaches > based on bootverbose. dmesg for device attaches seems mostly > redundant with devinfo(8) for persistent devices like ACPI CPU and > est(4). > > > The 'CPU XX Launched' messages are very useful for initial diagnostic > > of the SMP startup failures. You need to enable bootverbose to see the > > hang details, but for initial hint they are required. Unfortunately, AP > > startup hangs occur too often to pretend that this can be delegated to > > very specific circumstances. > > Really? I don't know that I've ever seen an AP startup hang. How > often do they occur? It was epidemic with Sandy Bridge, mostly correlated to specific BIOS supplier and its interaction with the x2APIC enablement, see madt.c:170 and below. There were several recent reports of the issue with Broadwell Xeon machines, no additional data or resolution. There are sporadic reports of the problem, where I do not see a clear commonality.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20180419214550.GF6887>