lkml.org 
[lkml]   [2018]   [Jan]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] x86/asm: Move 'status' from thread_struct to thread_info

* Andy Lutomirski <luto@kernel.org> wrote:

> The TS_COMPAT bit is very hot and is accessed from code paths that
> mostly also touch thread_info::flags. Move it into struct
> thread_info to improve cache locality.
>
> The only reason it was in thread_struct is that there was a brief
> period during which we didn't allow arch-specific fields in struct
> thread_info.
>
> Linus suggested further changing:
>
> ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
>
> to:
>
> if (unlikely(ti->status & (TS_COMPAT|TS_I386_REGS_POKED)))
> ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);
>
> on the theory that frequently dirtying the cacheline even in pure
> 64-bit code that never needs to modify status hurts performance.
> That could be a reasonable followup patch, but I suspect it matters
> less on top of this patch.
>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/entry/common.c | 4 ++--
> arch/x86/include/asm/processor.h | 2 --
> arch/x86/include/asm/syscall.h | 6 +++---
> arch/x86/include/asm/thread_info.h | 3 ++-
> arch/x86/kernel/process_64.c | 4 ++--
> arch/x86/kernel/ptrace.c | 2 +-
> arch/x86/kernel/signal.c | 2 +-
> 7 files changed, 11 insertions(+), 12 deletions(-)

Reviewed-by: Ingo Molnar <mingo@kernel.org>

Thanks,

Ingo

\
 
 \ /
  Last update: 2018-01-28 20:03    [W:0.070 / U:34.236 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site