linux-kernel - Re: [Patch v3 0/7] Optimize clear dirty log

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Date:   Mon, 20 Mar 2023 17:41:19 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vipin Sharma <vipinsh@...gle.com>
Cc:     pbonzini@...hat.com, bgardon@...gle.com, dmatlack@...gle.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v3 0/7] Optimize clear dirty log

On Fri, Mar 17, 2023, Sean Christopherson wrote:
> On Fri, Feb 10, 2023, Vipin Sharma wrote:
> > This patch series has optimized control flow of clearing dirty log and
> > improved its performance by ~40% (2% more than v2).
> > 
> > It also got rid of many variants of the handle_changed_spte family of
> > functions and converged logic to one handle_changed_spte() function. It
> > also remove tdp_mmu_set_spte_no_[acc_track|dirty_log] and various
> > booleans for controlling them.
> >
> > v3:
> > - Tried to do better job at writing commit messages.
> 
> LOL, that's the spirit!
> 
> Did a cursory glance, looks good.  I'll do a more thorough pass next week and get
> it queued up if all goes well.  No need for a v4 at this point, I'll fixup David's
> various nits when applying.

Ooof, that ended up being painful.  In hindsight, I should have asked for a v4,
but damage done, and it's my fault for throwing you a big blob of code in the
first place.

I ended up splitting the "interesting" patches into three each:

  1. Switch to the atomic-AND
  2. Drop the access-tracking / dirty-logging (as appropriate)
  3. Drop the call to __handle_changed_spte()

because logically they are three different things (although obviously related).

I have pushed the result to kvm-x86/mmu, but haven't merged to kvm-x86/next or
sent thanks because it's not yet tested.  I'll do testing tomorrow, but if you
can take a look in the meantime to make sure I didn't do something completely
boneheaded, it'd be much appreciated.