From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keith Owens <kaos@sgi.com>
Date: Tue, 31 Jan 2006 08:57:12 +0000
Subject: Re: [patch 1/6] align kenrel rbs on 128 byte
Message-Id: <6389.1138697832@kao2.melbourne.sgi.com>
List-Id: <linux-ia64.vger.kernel.org>
References: <200601310848.k0V8mbg11087@unix-os.sc.intel.com>
In-Reply-To: <200601310848.k0V8mbg11087@unix-os.sc.intel.com>
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To: linux-ia64@vger.kernel.org

"Chen, Kenneth W" (on Tue, 31 Jan 2006 00:48:28 -0800) wrote:
>The bottom of kernel rbs stack is the memory used to spill user
>dirty stack register partition when entering the kernel.  This
>space is heavily used on every kernel entry and exit. It deserve
>having its own dedicated cache line and not to share with tail
>end of thread_info which is not used heavily.
>
>Align the bottom of kernel rbs stack to 128 byte boundary.
>
>Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
>
>
>--- ./include/asm-ia64/ptrace.h.orig	2006-01-19 16:45:49.695591377 -0800
>+++ ./include/asm-ia64/ptrace.h	2006-01-20 02:24:05.985205410 -0800
>@@ -75,7 +75,7 @@
> # define KERNEL_STACK_SIZE_ORDER		0
> #endif
> 
>-#define IA64_RBS_OFFSET			((IA64_TASK_SIZE + IA64_THREAD_INFO_SIZE + 15) & ~15)
>+#define IA64_RBS_OFFSET			((IA64_TASK_SIZE + IA64_THREAD_INFO_SIZE + 127) & ~127)
> #define IA64_STK_OFFSET			((1 << KERNEL_STACK_SIZE_ORDER)*PAGE_SIZE)
> 
> #define KERNEL_STACK_SIZE		IA64_STK_OFFSET

The cache lines are not guaranteed to be 128 byte aligned, they were 64
on bigsur.  Change 127 to (L1_CACHE_BYTES - 1).