On 05/25/2011 05:09 AM, Takuya Yoshikawa wrote:
From: Takuya Yoshikawa<yoshikawa.takuya@xxxxxxxxxxxxx>
During tracing the emulator, we noticed that init_emulate_ctxt()
sometimes took a bit longer time than we expected.
This patch is for mitigating the problem by some degree.
By looking into the function, we soon notice that it clears the whole
decode_cache whose size is about 2.5K bytes now. Furthermore, most of
the bytes are taken for the two read_cache arrays, which are used only
by a few instructions.
Considering the fact that we are not assuming the cache arrays have
been cleared when we store actual data, we do not need to clear the
arrays: 2K bytes elimination. In addition, we can avoid clearing the
fetch_cache and regs arrays.
This patch changes the initialization not to clear the arrays.
On our 64-bit host, init_emulate_ctxt() becomes 0.3 to 0.5us faster with
this patch applied.
Thanks, applied.
It strikes me that initializing the emulator in x86.c is the wrong
thing. We should move the entire thing to x86_decode_insn().
We'll need a few more callbacks for that, though (register, eflags);
eventually we can read just registers that are used and write only
registers that were updated.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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