linux-kernel - Re: [PATCH 14/17] KVM: monolithic: x86: inline more exit handlers in vmx.c

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Message-ID: <3ec06895-d05d-aacd-17cc-08eedb21ccba@redhat.com>
Date:   Wed, 25 Sep 2019 09:52:52 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Andrea Arcangeli <aarcange@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Peter Xu <peterx@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 14/17] KVM: monolithic: x86: inline more exit handlers in
 vmx.c

On 24/09/19 03:55, Andrea Arcangeli wrote:
>> So it's forty bytes.  I think we can leave this out.
> This commit I reverted adds literally 3 inlines called by 3 functions,
> in a very fast path, how many bytes of .text difference did you expect
> by dropping some call/ret from a very fast path when you asked me to
> test it? I mean it's just a couple of insn each.

Actually I was either expecting the difference to be zero, meaning GCC
was already inlining them.

I think it is not inlining the functions because they are still
referenced by vmx_exit_handlers.  After patch 15 you could drop them
from the array, and then GCC should inline them.

Paolo