Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 24 Jun 2022 17:39:30 +0000
From:   David Matlack <dmatlack@google.com>
To:     Sean Christopherson <seanjc@google.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] KVM: x86/mmu: Buffer nested MMU split_desc_cache
 only by default capacity
Message-ID: <YrX20hfudgMQ/6ns@google.com>
References: <20220624171808.2845941-1-seanjc@google.com>
 <20220624171808.2845941-4-seanjc@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220624171808.2845941-4-seanjc@google.com>
Precedence: bulk

On Fri, Jun 24, 2022 at 05:18:08PM +0000, Sean Christopherson wrote:
> Buffer split_desc_cache, the cache used to allcoate rmap list entries,
> only by the default cache capacity (currently 40), not by doubling the
> minimum (513).  Aliasing L2 GPAs to L1 GPAs is uncommon, thus eager page
> splitting is unlikely to need 500+ entries.  And because each object is a
> non-trivial 128 bytes (see struct pte_list_desc), those extra ~500
> entries means KVM is in all likelihood wasting ~64kb of memory per VM.
> 
> Link: https://lore.kernel.org/all/YrTDcrsn0%2F+alpzf@google.com
> Cc: David Matlack <dmatlack@google.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Thanks for the cleanups!

Reviewed-by: David Matlack <dmatlack@google.com>