KVM: x86/mmu: Buffer nested MMU split_desc_cache only by default capacity

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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>
Message-Id: <20220624171808.2845941-4-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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Sean Christopherson 2022-06-24 17:18:08 +00:00 • committed by Paolo Bonzini

parent 72ae5822b8

commit b9b71f4368

1 changed files with 15 additions and 7 deletions

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arch/x86/kvm/mmu/mmu.c

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