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target-arm: Implement WFE as a yield operation

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Implement WFE to yield our timeslice to the next CPU.
This avoids slowdowns in multicore configurations caused
by one core busy-waiting on a spinlock which can't possibly
be unlocked until the other core has an opportunity to run.
This speeds up my test case A15 dual-core boot by a factor
of three (though it is still four or five times slower than
a single-core boot).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1393339545-22111-1-git-send-email-peter.maydell@linaro.org
Reviewed-by: Richard Henderson <rth@twiddle.net>
Tested-by: Rob Herring <rob.herring@linaro.org>
This commit is contained in:
Peter Maydell 2014-03-10 14:56:30 +00:00
parent 2b194951c5
commit 72c1d3af6e
5 changed files with 19 additions and 0 deletions
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1
include/exec/cpu-defs.h
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@ -59,6 +59,7 @@ typedef uint64_t target_ulong;
#define EXCP_HLT 0x10001 /* hlt instruction reached */
#define EXCP_DEBUG 0x10002 /* cpu stopped after a breakpoint or singlestep */
#define EXCP_HALTED 0x10003 /* cpu is halted (waiting for external event) */
#define EXCP_YIELD 0x10004 /* cpu wants to yield timeslice to another */
#define TB_JMP_CACHE_BITS 12
#define TB_JMP_CACHE_SIZE (1 << TB_JMP_CACHE_BITS)