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Groups > linux.kernel > #1358777

[PATCH] Revert "arm64: Increase the max granular size"

From Ganesh Mahendran <opensource.ganesh@gmail.com>
Newsgroups linux.kernel
Subject [PATCH] Revert "arm64: Increase the max granular size"
Date 2016-03-16 11:00 +0100
Message-ID <rdgpb-7eq-1@gated-at.bofh.it> (permalink)
Organization linux.* mail to news gateway

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Reverts commit 97303480753e ("arm64: Increase the max granular size").

The commit 97303480753e ("arm64: Increase the max granular size") will
degrade system performente in some cpus.

We test wifi network throughput with iperf on Qualcomm msm8996 CPU:
----------------
run on host:
  # iperf -s
run on device:
  # iperf -c <device-ip-addr> -t 100 -i 1
----------------

Test result:
----------------
with commit 97303480753e ("arm64: Increase the max granular size"):
    172MBits/sec

without commit 97303480753e ("arm64: Increase the max granular size"):
    230MBits/sec
----------------

Some module like slab/net will use the L1_CACHE_SHIFT, so if we do not
set the parameter correctly, it may affect the system performance.

So revert the commit.

Cc: stable@vger.kernel.org
Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
---
 arch/arm64/include/asm/cache.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cache.h b/arch/arm64/include/asm/cache.h
index 5082b30..bde4499 100644
--- a/arch/arm64/include/asm/cache.h
+++ b/arch/arm64/include/asm/cache.h
@@ -18,7 +18,7 @@
 
 #include <asm/cachetype.h>
 
-#define L1_CACHE_SHIFT		7
+#define L1_CACHE_SHIFT		6
 #define L1_CACHE_BYTES		(1 << L1_CACHE_SHIFT)
 
 /*
-- 
1.7.9.5

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[PATCH] Revert "arm64: Increase the max granular size" Ganesh Mahendran <opensource.ganesh@gmail.com> - 2016-03-16 11:00 +0100
  Re: [PATCH] Revert "arm64: Increase the max granular size" Will Deacon <will.deacon@arm.com> - 2016-03-16 11:10 +0100
    Re: [PATCH] Revert "arm64: Increase the max granular size" Timur Tabi <timur@codeaurora.org> - 2016-03-16 14:10 +0100
      Re: [PATCH] Revert "arm64: Increase the max granular size" Mark Rutland <mark.rutland@arm.com> - 2016-03-16 15:10 +0100
        Re: [PATCH] Revert "arm64: Increase the max granular size" Will Deacon <will.deacon@arm.com> - 2016-03-16 15:40 +0100
          Re: [PATCH] Revert "arm64: Increase the max granular size" Mark Rutland <mark.rutland@arm.com> - 2016-03-16 16:00 +0100
      Re: [PATCH] Revert "arm64: Increase the max granular size" Catalin Marinas <catalin.marinas@arm.com> - 2016-03-16 15:20 +0100
        Re: [PATCH] Revert "arm64: Increase the max granular size" Timur Tabi <timur@codeaurora.org> - 2016-03-16 16:30 +0100
          Re: [PATCH] Revert "arm64: Increase the max granular size" Catalin Marinas <catalin.marinas@arm.com> - 2016-03-17 15:30 +0100
            Re: [PATCH] Revert "arm64: Increase the max granular size" Timur Tabi <timur@codeaurora.org> - 2016-03-17 16:00 +0100
              Re: [PATCH] Revert "arm64: Increase the max granular size" Catalin Marinas <catalin.marinas@arm.com> - 2016-03-17 16:40 +0100
                Re: [PATCH] Revert "arm64: Increase the max granular size" Marc Zyngier <marc.zyngier@arm.com> - 2016-03-17 17:10 +0100

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