Re: [patch] compress the stack layout of do_page_fault(), x86
* Andi Kleen <[EMAIL PROTECTED]> wrote:
> On Sat, Jul 09, 2005 at 09:42:20PM +0200, Ingo Molnar wrote:
> >
> > * Andi Kleen <[EMAIL PROTECTED]> wrote:
> >
> > > Ingo Molnar <[EMAIL PROTECTED]> writes:
> > > >
> > > > +static void force_sig_info_fault(int si_signo, int si_code,
> > > > +unsigned long address, struct
> > > > task_struct *tsk)
> > >
> > > This won't work with a unit-at-a-time compiler which happily inlines
> > > everything static with only a single caller. Use noinline
> >
> > this function has two callers.
>
> Even then it's still better to mark it noinline, otherwise a different
> inlining algorithm in a new compiler might do the wrong thing. It's
> also useful documentation.
ok, agreed. Delta patch below.
Ingo
make force_sig_info_fault() noinline, suggested by Andi Kleen.
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
--- linux/arch/i386/mm/fault.c.orig
+++ linux/arch/i386/mm/fault.c
@@ -199,8 +199,8 @@ static inline int is_prefetch(struct pt_
return 0;
}
-static void force_sig_info_fault(int si_signo, int si_code,
-unsigned long address, struct task_struct *tsk)
+static noinline void force_sig_info_fault(int si_signo, int si_code,
+ unsigned long address, struct task_struct *tsk)
{
siginfo_t info;
-
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Re: [patch] compress the stack layout of do_page_fault(), x86
On Sat, Jul 09, 2005 at 09:42:20PM +0200, Ingo Molnar wrote: > > * Andi Kleen <[EMAIL PROTECTED]> wrote: > > > Ingo Molnar <[EMAIL PROTECTED]> writes: > > > > > > +static void force_sig_info_fault(int si_signo, int si_code, > > > + unsigned long address, struct task_struct *tsk) > > > > This won't work with a unit-at-a-time compiler which happily inlines > > everything static with only a single caller. Use noinline > > this function has two callers. Even then it's still better to mark it noinline, otherwise a different inlining algorithm in a new compiler might do the wrong thing. It's also useful documentation. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] compress the stack layout of do_page_fault(), x86
On Sat, Jul 09, 2005 at 04:41:16PM +0200, Ingo Molnar wrote: > this patch pushes the creation of a rare signal frame (SIGBUS or > SIGSEGV) into a separate function, thus saving stackspace in the > main do_page_fault() stackframe. The effect is 132 bytes less of > stack used by the typical do_page_fault() invocation - resulting in > a denser cache-layout. does the benefit actually show up anywhere? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] compress the stack layout of do_page_fault(), x86
On Sat, 2005-07-09 at 21:15 +0200, Andi Kleen wrote: > On Sat, Jul 09, 2005 at 07:31:04PM +0200, Arjan van de Ven wrote: > > On Sat, 2005-07-09 at 19:05 +0200, Andi Kleen wrote: > > > Ingo Molnar <[EMAIL PROTECTED]> writes: > > > > > > > > +static void force_sig_info_fault(int si_signo, int si_code, > > > > +unsigned long address, struct > > > > task_struct *tsk) > > > > > > This won't work with a unit-at-a-time compiler which happily > > > inlines everything static with only a single caller. Use noinline > > > > but the x86 kernel is -fno-unit-at-a-time for stack reasons ;) > > The gcc people are making noises of removing that. So eventually > it will need to go. the gcc people also fixed the stack usage on inlining (at least this specific class) in CVS HEAD so the "problem" is a lot smaller whenever they make it go away. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] compress the stack layout of do_page_fault(), x86
* Andi Kleen <[EMAIL PROTECTED]> wrote: > Ingo Molnar <[EMAIL PROTECTED]> writes: > > > > +static void force_sig_info_fault(int si_signo, int si_code, > > +unsigned long address, struct task_struct *tsk) > > This won't work with a unit-at-a-time compiler which happily inlines > everything static with only a single caller. Use noinline this function has two callers. Ingo - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] compress the stack layout of do_page_fault(), x86
On Sat, Jul 09, 2005 at 07:31:04PM +0200, Arjan van de Ven wrote: > On Sat, 2005-07-09 at 19:05 +0200, Andi Kleen wrote: > > Ingo Molnar <[EMAIL PROTECTED]> writes: > > > > > > +static void force_sig_info_fault(int si_signo, int si_code, > > > + unsigned long address, struct task_struct *tsk) > > > > This won't work with a unit-at-a-time compiler which happily > > inlines everything static with only a single caller. Use noinline > > but the x86 kernel is -fno-unit-at-a-time for stack reasons ;) The gcc people are making noises of removing that. So eventually it will need to go. Also some kernels are compiled with that option removed and it works just fine. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] compress the stack layout of do_page_fault(), x86
On Sat, 2005-07-09 at 19:05 +0200, Andi Kleen wrote: > Ingo Molnar <[EMAIL PROTECTED]> writes: > > > > +static void force_sig_info_fault(int si_signo, int si_code, > > +unsigned long address, struct task_struct *tsk) > > This won't work with a unit-at-a-time compiler which happily > inlines everything static with only a single caller. Use noinline but the x86 kernel is -fno-unit-at-a-time for stack reasons ;) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] compress the stack layout of do_page_fault(), x86
Ingo Molnar <[EMAIL PROTECTED]> writes: > > +static void force_sig_info_fault(int si_signo, int si_code, > + unsigned long address, struct task_struct *tsk) This won't work with a unit-at-a-time compiler which happily inlines everything static with only a single caller. Use noinline -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [patch] compress the stack layout of do_page_fault(), x86
Guillaume noticed a bug in the patch, si_signo should be used instead of
SIGSEGV. (doh) New patch below.
Ingo
-
this patch pushes the creation of a rare signal frame (SIGBUS or
SIGSEGV) into a separate function, thus saving stackspace in the main
do_page_fault() stackframe. The effect is 132 bytes less of stack used
by the typical do_page_fault() invocation - resulting in a denser
cache-layout.
(another minor effect is that in case of kernel crashes that come from a
pagefault, we add less space to the already existing frame, giving the
crash functions a slightly higher chance to do their stuff without
overflowing the stack.)
(the changes also result in slightly cleaner code.)
build and boot tested.
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
argument bugfix from "Guillaume C." <[EMAIL PROTECTED]>
Index: linux/arch/i386/mm/fault.c
===
--- linux.orig/arch/i386/mm/fault.c
+++ linux/arch/i386/mm/fault.c
@@ -201,6 +201,18 @@ static inline int is_prefetch(struct pt_
return 0;
}
+static void force_sig_info_fault(int si_signo, int si_code,
+unsigned long address, struct task_struct *tsk)
+{
+ siginfo_t info;
+
+ info.si_signo = si_signo;
+ info.si_errno = 0;
+ info.si_code = si_code;
+ info.si_addr = (void __user *)address;
+ force_sig_info(si_signo, &info, tsk);
+}
+
fastcall void do_invalid_op(struct pt_regs *, unsigned long);
/*
@@ -220,9 +232,8 @@ fastcall notrace void do_page_fault(stru
struct vm_area_struct * vma;
unsigned long address;
unsigned long page;
- int write;
- siginfo_t info;
-
+ int write, si_code;
+
/* get the address */
__asm__("movl %%cr2,%0":"=r" (address));
trace_special(regs->eip, error_code, address);
@@ -236,7 +247,7 @@ fastcall notrace void do_page_fault(stru
tsk = current;
- info.si_code = SEGV_MAPERR;
+ si_code = SEGV_MAPERR;
/*
* We fault-in kernel-space virtual memory on-demand. The
@@ -316,7 +327,7 @@ fastcall notrace void do_page_fault(stru
* we can handle it..
*/
good_area:
- info.si_code = SEGV_ACCERR;
+ si_code = SEGV_ACCERR;
write = 0;
switch (error_code & 3) {
default:/* 3: write, present */
@@ -390,11 +401,7 @@ bad_area_nosemaphore:
/* Kernel addresses are always protection faults */
tsk->thread.error_code = error_code | (address >= TASK_SIZE);
tsk->thread.trap_no = 14;
- info.si_signo = SIGSEGV;
- info.si_errno = 0;
- /* info.si_code has been set above */
- info.si_addr = (void __user *)address;
- force_sig_info(SIGSEGV, &info, tsk);
+ force_sig_info_fault(SIGSEGV, si_code, address, tsk);
return;
}
@@ -500,11 +507,7 @@ do_sigbus:
tsk->thread.cr2 = address;
tsk->thread.error_code = error_code;
tsk->thread.trap_no = 14;
- info.si_signo = SIGBUS;
- info.si_errno = 0;
- info.si_code = BUS_ADRERR;
- info.si_addr = (void __user *)address;
- force_sig_info(SIGBUS, &info, tsk);
+ force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
return;
vmalloc_fault:
-
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