[PATCH 00/12] thread_info cleanups and stack caching

From	Andy Lutomirski <luto@kernel.org>
Newsgroups	linux.kernel
Subject	[PATCH 00/12] thread_info cleanups and stack caching
Date	2016-09-13 23:30 +0200
Message-ID	<sh3rc-7o2-3@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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[Sorry this is late.  I apparently never hit enter on the git
 send-email command.  This is what I meant to send, except that I
 folded in the collect_syscall() fix and redid the rebase (which
 was uneventful).]

This series extensively cleans up thread_info.  thread_info has been
partially redundant with thread_struct for a long time -- both are
places for arch code to add additional per-task variables.
thread_struct is much cleaner: it's always in task_struct, and
there's nothing particularly magical about it.  So this series moves
x86's status field from thread_info to thread_struct and to remove
x86's dependence on thread_info's position on the stack.  Then it
opts x86 into a new config option THREAD_INFO_IN_TASK to get rid of
arch-specific thread_info entirely and simply embed a defanged
thread_info (containing only flags) and 'int cpu' into task_struct.

Once thread_info stops being magical, there's another benefit: we
can free the thread stack as soon as the task is dead (without
waiting for RCU) and then, if vmapped stacks are in use, cache the
entire stack for reuse on the same cpu.

This seems to be an overall speedup of about 0.5-1 µs per
pthread_create/join compared to the old CONFIG_VMAP_STACK=n baseline
in a simple test -- a percpu cache of vmalloced stacks appears to be
a bit faster than a high-order stack allocation, at least when the
cache hits.  (I expect that workloads with a low cache hit rate are
likely to be dominated by other effects anyway.)

Changes from before:
 - A bunch of the series is already in 4.8-rc.
 - Added the get_wchan() and collect_syscall() patches.
 - Rebased.

Andy Lutomirski (9):
  x86/asm: Move 'status' from struct thread_info to struct thread_struct
  sched: Allow putting thread_info into task_struct
  x86: Move thread_info into task_struct
  sched: Add try_get_task_stack() and put_task_stack()
  x86/dumpstack: Pin the target stack in save_stack_trace_tsk()
  x86/process: Pin the target stack in get_wchan()
  lib/syscall: Pin the task stack in collect_syscall()
  sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK
  fork: Cache two thread stacks per cpu if CONFIG_VMAP_STACK is set

Linus Torvalds (2):
  x86/entry: Get rid of pt_regs_to_thread_info()
  um: Stop conflating task_struct::stack with thread_info

Oleg Nesterov (1):
  kthread: to_live_kthread() needs try_get_task_stack()

 arch/x86/Kconfig                   |  1 +
 arch/x86/entry/common.c            | 24 ++++------
 arch/x86/entry/entry_64.S          |  7 ++-
 arch/x86/include/asm/processor.h   | 12 +++++
 arch/x86/include/asm/syscall.h     | 20 ++------
 arch/x86/include/asm/thread_info.h | 69 ++-------------------------
 arch/x86/kernel/asm-offsets.c      |  5 +-
 arch/x86/kernel/fpu/init.c         |  1 -
 arch/x86/kernel/irq_64.c           |  3 +-
 arch/x86/kernel/process.c          | 28 ++++++-----
 arch/x86/kernel/process_64.c       |  4 +-
 arch/x86/kernel/ptrace.c           |  2 +-
 arch/x86/kernel/signal.c           |  2 +-
 arch/x86/kernel/stacktrace.c       |  5 ++
 arch/x86/um/ptrace_32.c            |  8 ++--
 include/linux/init_task.h          | 11 +++++
 include/linux/sched.h              | 66 +++++++++++++++++++++++++-
 include/linux/thread_info.h        | 15 ++++++
 init/Kconfig                       | 10 ++++
 init/init_task.c                   |  7 ++-
 kernel/fork.c                      | 97 ++++++++++++++++++++++++++++++++++----
 kernel/kthread.c                   |  8 +++-
 kernel/sched/core.c                |  4 ++
 kernel/sched/sched.h               |  4 ++
 lib/syscall.c                      | 15 +++++-
 25 files changed, 286 insertions(+), 142 deletions(-)

-- 
2.7.4

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[PATCH 00/12] thread_info cleanups and stack caching Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:30 +0200
  [PATCH 03/12] um: Stop conflating task_struct::stack with thread_info Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:30 +0200
    Re: [PATCH 03/12] um: Stop conflating task_struct::stack with  thread_info Ingo Molnar <mingo@kernel.org> - 2016-09-15 08:30 +0200
    [tip:x86/asm] um/Stop conflating task_struct::stack with  thread_info tip-bot for Linus Torvalds <tipbot@zytor.com> - 2016-09-15 12:50 +0200
  [PATCH 12/12] fork: Cache two thread stacks per cpu if CONFIG_VMAP_STACK is set Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
  [PATCH 01/12] x86/asm: Move 'status' from struct thread_info to struct thread_struct Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
    [tip:x86/asm] x86/asm: Move the thread_info::status field to  thread_struct tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-09-15 12:50 +0200
  [PATCH 10/12] lib/syscall: Pin the task stack in collect_syscall() Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
  [PATCH 08/12] x86/dumpstack: Pin the target stack in save_stack_trace_tsk() Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
    Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Josh Poimboeuf <jpoimboe@redhat.com> - 2016-09-14 17:00 +0200
      Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in save_stack_trace_tsk() Andy Lutomirski <luto@amacapital.net> - 2016-09-14 20:30 +0200
        Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Josh Poimboeuf <jpoimboe@redhat.com> - 2016-09-14 20:40 +0200
          Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in save_stack_trace_tsk() Andy Lutomirski <luto@amacapital.net> - 2016-09-15 20:10 +0200
            Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Josh Poimboeuf <jpoimboe@redhat.com> - 2016-09-15 20:40 +0200
              Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in save_stack_trace_tsk() Andy Lutomirski <luto@amacapital.net> - 2016-09-15 20:50 +0200
                Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Josh Poimboeuf <jpoimboe@redhat.com> - 2016-09-15 21:20 +0200
                Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Peter Zijlstra <peterz@infradead.org> - 2016-09-16 09:50 +0200
                Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in save_stack_trace_tsk() Andy Lutomirski <luto@amacapital.net> - 2016-09-16 17:20 +0200
                Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in save_stack_trace_tsk() Andy Lutomirski <luto@kernel.org> - 2016-09-16 17:40 +0200
                Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Peter Zijlstra <peterz@infradead.org> - 2016-09-16 18:40 +0200
                Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Peter Zijlstra <peterz@infradead.org> - 2016-09-16 17:40 +0200
    Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Ingo Molnar <mingo@kernel.org> - 2016-09-15 08:40 +0200
      Re: [PATCH 08/12] x86/dumpstack: Pin the target stack in  save_stack_trace_tsk() Ingo Molnar <mingo@kernel.org> - 2016-09-15 11:30 +0200
  [PATCH 09/12] x86/process: Pin the target stack in get_wchan() Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
    Re: [PATCH 09/12] x86/process: Pin the target stack in get_wchan() Jann Horn <jann@thejh.net> - 2016-09-17 04:10 +0200
      Re: [PATCH 09/12] x86/process: Pin the target stack in get_wchan() Andy Lutomirski <luto@amacapital.net> - 2016-09-23 00:50 +0200
        Re: [PATCH 09/12] x86/process: Pin the target stack in get_wchan() Andy Lutomirski <luto@amacapital.net> - 2016-09-23 01:00 +0200
        Re: [PATCH 09/12] x86/process: Pin the target stack in get_wchan() Jann Horn <jann@thejh.net> - 2016-09-23 09:50 +0200
  [PATCH 06/12] sched: Add try_get_task_stack() and put_task_stack() Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
  [PATCH 02/12] x86/entry: Get rid of pt_regs_to_thread_info() Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
    Re: [PATCH 02/12] x86/entry: Get rid of pt_regs_to_thread_info() Ingo Molnar <mingo@kernel.org> - 2016-09-15 08:30 +0200
    [tip:x86/asm] x86/entry: Get rid of pt_regs_to_thread_info() tip-bot for Linus Torvalds <tipbot@zytor.com> - 2016-09-15 12:50 +0200
  [PATCH 05/12] x86: Move thread_info into task_struct Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
    [tip:x86/asm] x86: Move thread_info into task_struct tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-09-15 12:50 +0200
  [PATCH 04/12] sched: Allow putting thread_info into task_struct Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
    [tip:x86/asm] sched/core: Allow putting thread_info into  task_struct tip-bot for Andy Lutomirski <tipbot@zytor.com> - 2016-09-15 12:50 +0200
  [PATCH 11/12] sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200
  [PATCH 07/12] kthread: to_live_kthread() needs try_get_task_stack() Andy Lutomirski <luto@kernel.org> - 2016-09-13 23:40 +0200

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