On Tue, 2021-02-16 at 15:10 +, David Woodhouse wrote:
> Actually it breaks before that, in rcu_cpu_starting(). A spinlock
> around that, an atomic_t to let the APs do their TSC sync one at a time
> (both in the above tree now), and I have a 75% saving on CPU bringup
> time for my 28-thread
On Tue, 2021-02-16 at 13:53 +, David Woodhouse wrote:
> I threw it into my tree at
> https://git.infradead.org/users/dwmw2/linux.git/shortlog/refs/heads/parallel
>
> It seems to work fairly nicely. The parallel SIPI seems to win be about
> a third of the bringup time on my 28-thread Haswell
On Fri, 2021-02-12 at 18:30 +0100, Thomas Gleixner wrote:
> On Fri, Feb 12 2021 at 01:29, Thomas Gleixner wrote:
> > On Thu, Feb 11 2021 at 22:58, David Woodhouse wrote:
> > I have no problem with making that jump based. It does not matter at
> > all. But you can't use the idle task stack before
On Thu, 2021-01-21 at 15:55 +0100, Thomas Gleixner wrote:
> > Here's the hack we're testing with, for reference. It's kind of ugly
> > but you can see where it's going. Note that the CMOS mangling for the
> > warm reset vector is going to need to be lifted out of the per-cpu
> > loop, and done
On Thu, 2021-01-21 at 15:42 +, David Woodhouse wrote:
> [2.289283] BUG: kernel NULL pointer dereference, address:
> [2.289283] #PF: supervisor write access in kernel mode
> [2.289283] #PF: error_code(0x0002) - not-present page
> [2.289283] PGD 0 P4D 0
> [
On Thu, 2021-01-21 at 15:55 +0100, Thomas Gleixner wrote:
> > Testing on real hardware has been more interesting and less useful so
> > far. We started with the CPUHP_BRINGUP_KICK_CPU state being
> > *immediately* before CPUHP_BRINGUP_CPU. On my 28-thread Haswell box,
> > that didn't come up at
David,
On Tue, Jan 19 2021 at 12:12, David Woodhouse wrote:
> On Tue, 2020-12-15 at 22:20 +0100, Thomas Gleixner wrote:
> We've been playing with this a little. There's a proof-of-concept hack
> below; don't look too hard because it's only really for figuring out
> the timing etc.
>
> Basically
On Tue, 2020-12-15 at 22:20 +0100, Thomas Gleixner wrote:
> Since the rewrite of the CPU hotplug infrastructure to a state machine
> it's pretty obvious that the bringup of APs can changed from the fully
> serialized:
>
> for_each_present_cpu(cpu) {
> if (!cpu_online(cpu))
>
On Wed, 2020-12-16 at 16:31 +0100, Thomas Gleixner wrote:
> But obviously the C-state in which the APs are waiting is not really
> relevant, as you demonstrated that the cost is due to INIT/SIPI even
> with spinwait, which is what I suspected.
>
> OTOH, the advantage of INIT/SIPI is that the AP
在 2020/12/16 23:31, Thomas Gleixner 写道:
OTOH, the advantage of INIT/SIPI is that the AP comes up in a well known
state.
We can set APs to a known state explicitly like BSP will do in kexec
case (what we also tried
to do in the patch). Maybe it is not a big problem?
Best regards
Kai
Kai,
On Wed, Dec 16 2020 at 22:18, shenkai wrote:
> After some tests, the conclusion that time cost is from deep C-state
> turns out to be wrong
>
> Sorry for that.
No problem.
> In kexec case, first let APs spinwait like what I did in that patch,
> but wake APs up by sending apic INIT and
在 2020/12/16 18:12, Thomas Gleixner 写道:
Kai,
On Wed, Dec 16 2020 at 16:45, shenkai wrote:
在 2020/12/16 5:20, Thomas Gleixner 写道:
Thanks for your and Andy's precious comments. I would like to take a try on
reconstructing this patch to make it more decent and generic.
It would be
Kai,
On Wed, Dec 16 2020 at 16:45, shenkai wrote:
> 在 2020/12/16 5:20, Thomas Gleixner 写道:
>>
>>
> Thanks for your and Andy's precious comments. I would like to take a try on
>
> reconstructing this patch to make it more decent and generic.
>> It would be interesting to see the numbers just with
在 2020/12/16 5:20, Thomas Gleixner 写道:
On Tue, Dec 15 2020 at 08:31, Andy Lutomirski wrote:
On Tue, Dec 15, 2020 at 6:46 AM shenkai (D) wrote:
From: shenkai
Date: Tue, 15 Dec 2020 01:58:06 +
Subject: [PATCH] use x86 cpu park to speedup smp_init in kexec situation
In kexec reboot on x86
On Tue, Dec 15 2020 at 08:31, Andy Lutomirski wrote:
> On Tue, Dec 15, 2020 at 6:46 AM shenkai (D) wrote:
>>
>> From: shenkai
>> Date: Tue, 15 Dec 2020 01:58:06 +
>> Subject: [PATCH] use x86 cpu park to speedup smp_init in kexec situation
>>
>> In kexec reboot on x86 machine, APs will be
On Tue, Dec 15, 2020 at 6:46 AM shenkai (D) wrote:
>
> From: shenkai
> Date: Tue, 15 Dec 2020 01:58:06 +
> Subject: [PATCH] use x86 cpu park to speedup smp_init in kexec situation
>
> In kexec reboot on x86 machine, APs will be halted and then waked up
> by the apic INIT and SIPI interrupt.
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