[RFC PATCH 0/4] KVM: emulator: speed up instruction fetch

[Paolo Bonzini]

This small series provides another ~6% speedup on top of Bandan's patches.
It does so by speeding up instruction fetches.  The three tricks, one per
patch, are to help the compiler a bit by redistributing the work between
do_insn_fetch_byte and do_insn_fetch, to avoid repeated checks on the
boundary of the fetch cache, and to exploit the processor's support for
unaligned accesses.

Before:
   819 cycles/emulated jump instruction
   1020 cycles/emulated move instruction
   1026 cycles/emulated arithmetic instruction
   1264 cycles/emulated memory load instruction
   1182 cycles/emulated memory store instruction
   1299 cycles/emulated memory RMW instruction

After:
   771 cycles/emulated jump instruction
   963 cycles/emulated move instruction
   960 cycles/emulated arithmetic instruction
   1192 cycles/emulated memory load instruction
   1110 cycles/emulated memory store instruction
   1228 cycles/emulated memory RMW instruction

Paolo Bonzini (4):
  KVM: emulate: speed up do_insn_fetch
  KVM: emulate: avoid repeated calls to do_insn_fetch_bytes
  KVM: emulate: avoid per-byte copying in instruction fetches
  KVM: emulate: put pointers in the fetch_cache

 arch/x86/include/asm/kvm_emulate.h |  4 +-
 arch/x86/kvm/emulate.c             | 97 ++++++++++++++++++++------------------
 arch/x86/kvm/trace.h               |  6 +--
 3 files changed, 57 insertions(+), 50 deletions(-)

-- 
1.8.3.1

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