linux-kernel - Re: [PATCH v2 9/9] KVM: X86: Optimize zapping rmap

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Message-ID: <c2c83189-6bc4-1f3b-36da-be19b940dcf9@redhat.com>
Date:   Thu, 29 Jul 2021 11:35:04 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH v2 9/9] KVM: X86: Optimize zapping rmap

On 29/07/21 00:31, Sean Christopherson wrote:
>> If that'll be a performance concern, no objection to hard code it.
> It's more about unnecessary complexity than it is about performance, e.g. gcc-10
> generates identical code for both version (which did surprise the heck out of me).

If you think of what's needed to produce decent (as fast as C) code out 
of STL code, that's not surprising. :)  Pretty cool that it lets people 
write nicer C code too, though.

> If we really want to isolate pte_list_destroy(), I would vote for something like
> this (squashed in).   pte_list_remove() already calls mmu_spte_clear_track_bits(),
> so that particular separation of concerns has already gone out the window.

Yes, that's fair enough.  Thanks for the review!

Paolo