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| author | Peter Maydell <peter.maydell@linaro.org> | 2014-05-13 16:09:38 +0100 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2014-05-13 16:09:38 +0100 |
| commit | 2f0d8631b74c873c8867a7b509335bc2bf8d8886 (patch) | |
| tree | a3f384c8b4bfc7adba1ed83d1de2f94affe6ed06 | |
| parent | 2e1198672759eda6e122ff38fcf6df06f27e0fe2 (diff) | |
| download | qemu-2f0d8631b74c873c8867a7b509335bc2bf8d8886.zip qemu-2f0d8631b74c873c8867a7b509335bc2bf8d8886.tar.gz qemu-2f0d8631b74c873c8867a7b509335bc2bf8d8886.tar.bz2 | |
target-arm/helper.c: Don't flush the TLB if SCTLR is rewritten unchanged
Linux makes a habit of writing the same value to the SCTLR that it
already holds. In a sample boot of the kernel to a shell prompt
it wrote the SCTLR with the value it already held 325465 times,
and wrote different values just 3 times.
Skip flushing the TLB if the SCTLR value isn't actually being changed;
this speeds up my sample boot by 3-5%.
Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Reviewed-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1399560029-19007-1-git-send-email-peter.maydell@linaro.org
| -rw-r--r-- | target-arm/helper.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/target-arm/helper.c b/target-arm/helper.c index 3be917c..417161e 100644 --- a/target-arm/helper.c +++ b/target-arm/helper.c @@ -2081,6 +2081,13 @@ static void sctlr_write(CPUARMState *env, const ARMCPRegInfo *ri, { ARMCPU *cpu = arm_env_get_cpu(env); + if (env->cp15.c1_sys == value) { + /* Skip the TLB flush if nothing actually changed; Linux likes + * to do a lot of pointless SCTLR writes. + */ + return; + } + env->cp15.c1_sys = value; /* ??? Lots of these bits are not implemented. */ /* This may enable/disable the MMU, so do a TLB flush. */ |