linux-kernel - Re: [PATCH] pvclock: introduce seqcount-like API

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Message-ID: <3bfffd0d-bb91-d9e3-b67b-a82be9cb82d7@redhat.com>
Date:	Thu, 9 Jun 2016 20:03:02 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Roman Kagan <rkagan@...tuozzo.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm list <kvm@...r.kernel.org>,
	Minfei Huang <mnghuan@...il.com>,
	Andrew Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] pvclock: introduce seqcount-like API



On 09/06/2016 19:12, Andy Lutomirski wrote:
> On Thu, Jun 9, 2016 at 6:45 AM, Paolo Bonzini <pbonzini@...hat.com> wrote:
>> On 09/06/2016 15:35, Roman Kagan wrote:
>>> On Thu, Jun 09, 2016 at 02:47:54PM +0200, Paolo Bonzini wrote:
>>>> On 09/06/2016 14:43, Roman Kagan wrote:
>>> Has it landed in any public tree?  I'm unable to find any.  There
>>> appears to be another version of the patch on the list, so I'm confused.
>>
>> I'm about to push it to kvm/master.
> 
> Sorry for being slow.  I'm catching up.  In its current form, I don't
> like this patch.  Please don't apply it.

Sure, I was talking about Minfei's patches, not this one. :)  Of course
I need ack for this one.

> The problem is that this makes two significant changes at once:
> 
> 1. Use the new version helpers.  I like that change.
> 
> 2. Use __pvclock_read_cycles.  That should be separate, and it should
> come with timing numbers in the changelog.

__pvclock_read_cycles is pretty much the same as the code that is being
inlined.  Thus the only change is that __pvclock_read_cycles is called
inside the loop rather than outside, but the loop really is expected to
never roll so why make a copy in the first place?

I'll split the patch anyway, thanks!

Paolo