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[Qemu-devel] [PULL 10/17] target-arm/helper.c: Don't flush the TLB if SC
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PULL 10/17] target-arm/helper.c: Don't flush the TLB if SCTLR is rewritten unchanged |
Date: |
Tue, 13 May 2014 16:31:32 +0100 |
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 <address@hidden>
Reviewed-by: Laurent Desnogues <address@hidden>
Signed-off-by: Peter Maydell <address@hidden>
Message-id: address@hidden
---
target-arm/helper.c | 7 +++++++
1 file changed, 7 insertions(+)
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. */
--
1.9.2
- [Qemu-devel] [PULL 00/17] target-arm queue, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 17/17] hw/arm/omap_gpmc: Avoid buffer overrun filling prefetch FIFO, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 12/17] hw/net/cadence_gem: Remove dead code, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 09/17] hw/net/stellaris_enet: Convert to vmstate, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 15/17] hw/timer/exynos4210_mct: Avoid overflow in exynos4210_ltick_recalc_count, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 03/17] hw/net/stellaris_enet: Restructure tx_fifo code to avoid buffer overrun, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 14/17] hw/dma/omap_dma: Add (uint32_t) casts when shifting uint16_t by 16, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 16/17] hw/arm/stellaris: Correct handling of GPTM TAR register, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 10/17] target-arm/helper.c: Don't flush the TLB if SCTLR is rewritten unchanged,
Peter Maydell <=
- [Qemu-devel] [PULL 13/17] hw/arm/omap1: Avoid unintended sign extension writing omap_rtc YEARS_REG, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 11/17] hw/intc/allwinner-a10-pic: Add missing 'break', Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 06/17] hw/net/stellaris_enet: Correctly implement the TR and THR registers, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 05/17] hw/net/stellaris_enet: Rewrite tx fifo handling code, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 08/17] hw/net/stellaris_enet: Get rid of rx_fifo pointer, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 04/17] hw/net/stellaris_enet: Correct handling of packet padding, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 07/17] hw/net/stellaris_enet: Fix debug format strings, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 01/17] disas/libvixl: Update to libvixl 1.4, Peter Maydell, 2014/05/13
- [Qemu-devel] [PULL 02/17] savevm: Remove all the unneeded version_minimum_id_old (arm), Peter Maydell, 2014/05/13
- Re: [Qemu-devel] [PULL 00/17] target-arm queue, Peter Maydell, 2014/05/15