On Thu, 22 Apr 2021 15:38:53 +0200
Martin Pieuchot <m...@openbsd.org> wrote:
> Diff below remove the KERNEL_LOCK()/UNLOCK() dance from uvm_fault() for
> both amd64 and sparc64. That means the kernel lock will only be taken
> for lower faults and some amap/anon code will now run without it.
I made a similar diff, below, for macppc and powerpc64. In my small
trials, the build times were about the same on my 4-core powerpc64 and
slightly faster on my 2-core macppc.
My macppc kernel had a problem: it froze at boot, but the problem went
away after I reordered the kernel. In my guess, this unlocking diff
isn't the cause of the problem, because the freeze was too early
(before copyright); the other cpu wouldn't have entered the kernel, so
the kernel lock wouldn't prevent the freeze.
My powerpc64 trial was "make -j4" in src/gnu/usr.bin/clang on 4-core
POWER9 in Talos II. Before diff:
117m45.96s real 361m58.87s user 68m44.66s system
After diff:
115m24.53s real 362m02.65s user 58m40.99s system
I see that system time went down by 10 minutes, but real time is about
the same (down by 2 minutes).
My macppc trial was "dpb devel/cmake" on 2-cpu Power Mac G5.
Before diff: 03:44:50
After diff: 03:33:44
Real time went down by 11 minutes. Maybe the unlocking diff works
better on a 2-core machine, or maybe the unlocking diff does nothing
and I saved 11 minutes by random luck.
--George
Index: arch/powerpc/powerpc/trap.c
===================================================================
RCS file: /cvs/src/sys/arch/powerpc/powerpc/trap.c,v
retrieving revision 1.119
diff -u -p -r1.119 trap.c
--- arch/powerpc/powerpc/trap.c 11 Mar 2021 11:16:59 -0000 1.119
+++ arch/powerpc/powerpc/trap.c 28 Apr 2021 02:49:44 -0000
@@ -282,9 +282,7 @@ trap(struct trapframe *frame)
else
ftype = PROT_READ;
- KERNEL_LOCK();
error = uvm_fault(map, trunc_page(va), 0, ftype);
- KERNEL_UNLOCK();
if (error == 0)
return;
@@ -318,10 +316,8 @@ trap(struct trapframe *frame)
} else
vftype = ftype = PROT_READ;
- KERNEL_LOCK();
error = uvm_fault(&p->p_vmspace->vm_map,
trunc_page(frame->dar), 0, ftype);
- KERNEL_UNLOCK();
if (error == 0) {
uvm_grow(p, frame->dar);
@@ -343,10 +339,8 @@ trap(struct trapframe *frame)
ftype = PROT_READ | PROT_EXEC;
- KERNEL_LOCK();
error = uvm_fault(&p->p_vmspace->vm_map,
trunc_page(frame->srr0), 0, ftype);
- KERNEL_UNLOCK();
if (error == 0) {
uvm_grow(p, frame->srr0);
Index: arch/powerpc64/powerpc64/trap.c
===================================================================
RCS file: /cvs/src/sys/arch/powerpc64/powerpc64/trap.c,v
retrieving revision 1.49
diff -u -p -r1.49 trap.c
--- arch/powerpc64/powerpc64/trap.c 9 Jan 2021 13:14:02 -0000 1.49
+++ arch/powerpc64/powerpc64/trap.c 24 Apr 2021 03:21:02 -0000
@@ -126,9 +126,7 @@ trap(struct trapframe *frame)
access_type = PROT_READ | PROT_WRITE;
else
access_type = PROT_READ;
- KERNEL_LOCK();
error = uvm_fault(map, trunc_page(va), 0, access_type);
- KERNEL_UNLOCK();
if (error == 0)
return;
@@ -237,9 +235,7 @@ trap(struct trapframe *frame)
access_type = PROT_READ | PROT_WRITE;
else
access_type = PROT_READ;
- KERNEL_LOCK();
error = uvm_fault(map, trunc_page(va), 0, access_type);
- KERNEL_UNLOCK();
if (error == 0)
uvm_grow(p, va);
@@ -284,9 +280,7 @@ trap(struct trapframe *frame)
map = &p->p_vmspace->vm_map;
va = frame->srr0;
access_type = PROT_READ | PROT_EXEC;
- KERNEL_LOCK();
error = uvm_fault(map, trunc_page(va), 0, access_type);
- KERNEL_UNLOCK();
if (error == 0)
uvm_grow(p, va);
