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Message-ID: <1306244999.1999.5.camel@castor.rsk>
Date: Tue, 24 May 2011 14:49:59 +0100
From: Richard Kennedy <richard@....demon.co.uk>
To: Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>
Cc: lkml <linux-kernel@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>, wilsons@...rt.ca
Subject: [PATCH] x86: reorder mm_context_t to remove x86_64 alignment
padding & so shrink mm_struct
Reorder mm_context_t to remove alignment padding on 64 bit builds
shrinking its size from 64 to 56 bytes.
This allows mm_struct to shrink from 840 to 832 bytes, so using one
fewer cache lines, and getting more objects per slab when using slub.
slabinfo mm_struct reports
before :-
Sizes (bytes) Slabs
-----------------------------------
Object : 840 Total : 7
SlabObj: 896 Full : 1
SlabSiz: 16384 Partial: 4
Loss : 56 CpuSlab: 2
Align : 64 Objects: 18
after :-
Sizes (bytes) Slabs
----------------------------------
Object : 832 Total : 7
SlabObj: 832 Full : 1
SlabSiz: 16384 Partial: 4
Loss : 0 CpuSlab: 2
Align : 64 Objects: 19
Signed-off-by: Richard Kennedy <richard@....demon.co.uk>
---
patch against v2.6.39
compiled & tested on x86_64.
regards
Richard
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index aeff3e8..5f55e69 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -11,14 +11,14 @@
typedef struct {
void *ldt;
int size;
- struct mutex lock;
- void *vdso;
#ifdef CONFIG_X86_64
/* True if mm supports a task running in 32 bit compatibility mode. */
unsigned short ia32_compat;
#endif
+ struct mutex lock;
+ void *vdso;
} mm_context_t;
#ifdef CONFIG_SMP
--
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