Date: Sat, 21 Apr 2018 20:30:12 +0000 From: Colin Percival <cperciva@tarsnap.com> To: Warner Losh <imp@bsdimp.com>, gljennjohn@gmail.com Cc: Konstantin Belousov <kib@freebsd.org>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, Conrad Meyer <cem@freebsd.org> Subject: Re: RFC: Hiding per-CPU kernel output behind bootverbose Message-ID: <01000162e9e66234-e005d59e-2896-436a-aab1-a3d7b3a74610-000000@email.amazonses.com> In-Reply-To: <CANCZdfpi7fZky9VC_TZWhm4uuwnV1N=m3pO1MmDs9GKYJZgSwg@mail.gmail.com> References: <01000162df15f856-1e5d2641-2a72-4250-8d8e-adcd47bc5db4-000000@email.amazonses.com> <20180419204405.GE6887@kib.kiev.ua> <CAG6CVpUerOo%2B55nJq61Hy83RYpbOZS6puEDuemspfNS12urZZw@mail.gmail.com> <20180419214550.GF6887@kib.kiev.ua> <01000162e58a466e-98f0305b-1723-467a-bc49-342c3fa9fc5b-000000@email.amazonses.com> <20180421092049.GM6887@kib.kiev.ua> <20180421123544.56d7e690@ernst.home> <CANCZdfpi7fZky9VC_TZWhm4uuwnV1N=m3pO1MmDs9GKYJZgSwg@mail.gmail.com>
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On 04/21/18 12:52, Warner Losh wrote:
> On Sat, 21 Apr 2018 12:20:49 +0300
> Konstantin Belousov <kib@freebsd.org <mailto:kib@freebsd.org>> wrote:
> > On Sat, Apr 21, 2018 at 12:11:07AM +0000, Colin Percival wrote:
> > > Would it be sufficient for debugging purposes if I change the !bootverbose
> > > case from printing many lines of
> > >
> > > SMP: AP CPU #N Launched!
> > >
> > > to instead have a single
> > >
> > > SMP: Launching AP CPUs: 86 73 111 21 8 77 100 28 57 42 10 60 87 [...]
> > >
> > > ? (With each AP printing its number as it reaches the appropriate point?)
> > I am fine with the behaviour, but I am not sure how would you implement
> > this. printf(9) buffers the output, you need to flush it somehow.
>
> I don't think either of these is true (the double buffered part,. nor the
> buffered part). Well, they are both kinda true, but they don't matter. It's
> all to make dmesg and friends work. There's other issues, but at this stage of
> the boot we're single threaded and the CPUs that are launching take out a spin
> lock.
I just checked (by adding a 500 ms delay after each CPU prints its ID) and I
can definitely see the individual numbers being printed on the console.
> diff --git a/sys/x86/x86/mp_x86.c b/sys/x86/x86/mp_x86.c
> index 3fcf7aa25152..06973b1ea6d5 100644
> --- a/sys/x86/x86/mp_x86.c
> +++ b/sys/x86/x86/mp_x86.c
> @@ -1020,7 +1020,7 @@ init_secondary_tail(void)
> smp_cpus++;
>
> CTR1(KTR_SMP, "SMP: AP CPU #%d Launched", cpuid);
> - printf("SMP: AP CPU #%d Launched!\n", cpuid);
> + printf("%d%s", cpuid, smp_cpus == mp_ncpus ? "\n" : " ");
>
> /* Determine if we are a logical CPU. */
> if (cpu_info[PCPU_GET(apic_id)].cpu_hyperthread)
>
> is enough to give them all to me on a single line. We'd need another printf
> that says 'Starting APs: ' since otherwise we see:
>
> andom: unblocking device.
> ioapic0 <Version 2.0> irqs 0-23 on motherboard
> ioapic1 <Version 2.0> irqs 24-47 on motherboard
> 1 8 10 20 2 19 11 12 22 4 14 23 16 13 3 18 5 17 21 9 15 6 7
> Timecounter "TSC-low" frequency 1350029824 Hz quality 1000
>
> which doesn't make a lot of sense.
>
> Comments?
Here's the patch I have, which prints a header before the CPU IDs:
Index: sys/x86/x86/mp_x86.c
===================================================================
--- sys/x86/x86/mp_x86.c (revision 332638)
+++ sys/x86/x86/mp_x86.c (working copy)
@@ -1020,7 +1020,9 @@
smp_cpus++;
CTR1(KTR_SMP, "SMP: AP CPU #%d Launched", cpuid);
- printf("SMP: AP CPU #%d Launched!\n", cpuid);
+ printf(" %d", cpuid);
+ if (smp_cpus == mp_ncpus)
+ printf("\n");
/* Determine if we are a logical CPU. */
if (cpu_info[PCPU_GET(apic_id)].cpu_hyperthread)
@@ -1508,6 +1510,7 @@
if (mp_ncpus == 1)
return;
+ printf("SMP: Launching AP CPUs:");
atomic_store_rel_int(&aps_ready, 1);
while (smp_started == 0)
ia32_pause();
--
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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