Re: uvm_fault_lower refactoring
> Date: Tue, 23 Feb 2021 10:07:43 +0100
> From: Martin Pieuchot
>
> On 23/02/21(Tue) 00:24, Mark Kettenis wrote:
> > > Date: Mon, 22 Feb 2021 10:10:21 +0100
> > > From: Martin Pieuchot
> > >
> > > On 16/02/21(Tue) 11:20, Martin Pieuchot wrote:
> > > > Start by moving `pgo_fault' handler outside of uvm_fault_lower().
> > > >
> > > > If a page has a backing object that prefer to handler to fault itself
> > > > the locking will be different, so keep it under KERNEL_LOCK() for the
> > > > moment and make it separate from the rest of uvm_fault_lower().
> > > >
> > > > ok?
> > >
> > > Anyone?
> >
> > This diverges from NetBSD; you think that's a good idea?
>
> Which tree are you looking at? I'm doing this exactly to reduce
> differences with NetBSD. r1.228 of uvm_fault.c in NetBSD contain this
> logic in uvm_fault_internal().
Was looking at r1.221. So go ahead then.
> > > > Index: uvm/uvm_fault.c
> > > > ===
> > > > RCS file: /cvs/src/sys/uvm/uvm_fault.c,v
> > > > retrieving revision 1.115
> > > > diff -u -p -r1.115 uvm_fault.c
> > > > --- uvm/uvm_fault.c 16 Feb 2021 09:10:17 - 1.115
> > > > +++ uvm/uvm_fault.c 16 Feb 2021 10:13:58 -
> > > > @@ -598,10 +598,37 @@ uvm_fault(vm_map_t orig_map, vaddr_t vad
> > > > /* case 1: fault on an anon in our amap */
> > > > error = uvm_fault_upper(, , anons,
> > > > fault_type);
> > > > } else {
> > > > - /* case 2: fault on backing object or zero fill
> > > > */
> > > > - KERNEL_LOCK();
> > > > - error = uvm_fault_lower(, , pages,
> > > > fault_type);
> > > > - KERNEL_UNLOCK();
> > > > + struct uvm_object *uobj =
> > > > ufi.entry->object.uvm_obj;
> > > > +
> > > > + /*
> > > > +* if the desired page is not shadowed by the
> > > > amap and
> > > > +* we have a backing object, then we check to
> > > > see if
> > > > +* the backing object would prefer to handle
> > > > the fault
> > > > +* itself (rather than letting us do it with
> > > > the usual
> > > > +* pgo_get hook). the backing object signals
> > > > this by
> > > > +* providing a pgo_fault routine.
> > > > +*/
> > > > + if (uobj != NULL && uobj->pgops->pgo_fault !=
> > > > NULL) {
> > > > + KERNEL_LOCK();
> > > > + error = uobj->pgops->pgo_fault(,
> > > > + flt.startva, pages, flt.npages,
> > > > + flt.centeridx, fault_type,
> > > > flt.access_type,
> > > > + PGO_LOCKED);
> > > > + KERNEL_UNLOCK();
> > > > +
> > > > + if (error == VM_PAGER_OK)
> > > > + error = 0;
> > > > + else if (error == VM_PAGER_REFAULT)
> > > > + error = ERESTART;
> > > > + else
> > > > + error = EACCES;
> > > > + } else {
> > > > + /* case 2: fault on backing obj or zero
> > > > fill */
> > > > + KERNEL_LOCK();
> > > > + error = uvm_fault_lower(, ,
> > > > pages,
> > > > + fault_type);
> > > > + KERNEL_UNLOCK();
> > > > + }
> > > > }
> > > > }
> > > >
> > > > @@ -1054,26 +1081,6 @@ uvm_fault_lower(struct uvm_faultinfo *uf
> > > > struct vm_anon *anon = NULL;
> > > > vaddr_t currva;
> > > > voff_t uoff;
> > > > -
> > > > - /*
> > > > -* if the desired page is not shadowed by the amap and we have a
> > > > -* backing object, then we check to see if the backing object
> > > > would
> > > > -* prefer to handle the fault itself (rather than letting us do
> > > > it
> > > > -* with the usual pgo_get hook). the backing object signals
> > > > this by
> > > > -* providing a pgo_fault routine.
> > > > -*/
> > > > - if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > > > - result = uobj->pgops->pgo_fault(ufi, flt->startva,
> > > > pages,
> > > > - flt->npages, flt->centeridx, fault_type,
> > > > flt->access_type,
> > > > - PGO_LOCKED);
> > > > -
> > > > - if (result == VM_PAGER_OK)
> > > > - return (0); /* pgo_fault did pmap
> > > > enter */
> > > > -
Re: uvm_fault_lower refactoring
On 23/02/21(Tue) 00:24, Mark Kettenis wrote:
> > Date: Mon, 22 Feb 2021 10:10:21 +0100
> > From: Martin Pieuchot
> >
> > On 16/02/21(Tue) 11:20, Martin Pieuchot wrote:
> > > Start by moving `pgo_fault' handler outside of uvm_fault_lower().
> > >
> > > If a page has a backing object that prefer to handler to fault itself
> > > the locking will be different, so keep it under KERNEL_LOCK() for the
> > > moment and make it separate from the rest of uvm_fault_lower().
> > >
> > > ok?
> >
> > Anyone?
>
> This diverges from NetBSD; you think that's a good idea?
Which tree are you looking at? I'm doing this exactly to reduce
differences with NetBSD. r1.228 of uvm_fault.c in NetBSD contain this
logic in uvm_fault_internal().
> > > Index: uvm/uvm_fault.c
> > > ===
> > > RCS file: /cvs/src/sys/uvm/uvm_fault.c,v
> > > retrieving revision 1.115
> > > diff -u -p -r1.115 uvm_fault.c
> > > --- uvm/uvm_fault.c 16 Feb 2021 09:10:17 - 1.115
> > > +++ uvm/uvm_fault.c 16 Feb 2021 10:13:58 -
> > > @@ -598,10 +598,37 @@ uvm_fault(vm_map_t orig_map, vaddr_t vad
> > > /* case 1: fault on an anon in our amap */
> > > error = uvm_fault_upper(, , anons, fault_type);
> > > } else {
> > > - /* case 2: fault on backing object or zero fill */
> > > - KERNEL_LOCK();
> > > - error = uvm_fault_lower(, , pages, fault_type);
> > > - KERNEL_UNLOCK();
> > > + struct uvm_object *uobj = ufi.entry->object.uvm_obj;
> > > +
> > > + /*
> > > + * if the desired page is not shadowed by the amap and
> > > + * we have a backing object, then we check to see if
> > > + * the backing object would prefer to handle the fault
> > > + * itself (rather than letting us do it with the usual
> > > + * pgo_get hook). the backing object signals this by
> > > + * providing a pgo_fault routine.
> > > + */
> > > + if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > > + KERNEL_LOCK();
> > > + error = uobj->pgops->pgo_fault(,
> > > + flt.startva, pages, flt.npages,
> > > + flt.centeridx, fault_type, flt.access_type,
> > > + PGO_LOCKED);
> > > + KERNEL_UNLOCK();
> > > +
> > > + if (error == VM_PAGER_OK)
> > > + error = 0;
> > > + else if (error == VM_PAGER_REFAULT)
> > > + error = ERESTART;
> > > + else
> > > + error = EACCES;
> > > + } else {
> > > + /* case 2: fault on backing obj or zero fill */
> > > + KERNEL_LOCK();
> > > + error = uvm_fault_lower(, , pages,
> > > + fault_type);
> > > + KERNEL_UNLOCK();
> > > + }
> > > }
> > > }
> > >
> > > @@ -1054,26 +1081,6 @@ uvm_fault_lower(struct uvm_faultinfo *uf
> > > struct vm_anon *anon = NULL;
> > > vaddr_t currva;
> > > voff_t uoff;
> > > -
> > > - /*
> > > - * if the desired page is not shadowed by the amap and we have a
> > > - * backing object, then we check to see if the backing object would
> > > - * prefer to handle the fault itself (rather than letting us do it
> > > - * with the usual pgo_get hook). the backing object signals this by
> > > - * providing a pgo_fault routine.
> > > - */
> > > - if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > > - result = uobj->pgops->pgo_fault(ufi, flt->startva, pages,
> > > - flt->npages, flt->centeridx, fault_type, flt->access_type,
> > > - PGO_LOCKED);
> > > -
> > > - if (result == VM_PAGER_OK)
> > > - return (0); /* pgo_fault did pmap enter */
> > > - else if (result == VM_PAGER_REFAULT)
> > > - return ERESTART;/* try again! */
> > > - else
> > > - return (EACCES);
> > > - }
> > >
> > > /*
> > >* now, if the desired page is not shadowed by the amap and we have
> > >
> >
> >
Re: uvm_fault_lower refactoring
> Date: Mon, 22 Feb 2021 10:10:21 +0100
> From: Martin Pieuchot
>
> On 16/02/21(Tue) 11:20, Martin Pieuchot wrote:
> > Start by moving `pgo_fault' handler outside of uvm_fault_lower().
> >
> > If a page has a backing object that prefer to handler to fault itself
> > the locking will be different, so keep it under KERNEL_LOCK() for the
> > moment and make it separate from the rest of uvm_fault_lower().
> >
> > ok?
>
> Anyone?
This diverges from NetBSD; you think that's a good idea?
> > Index: uvm/uvm_fault.c
> > ===
> > RCS file: /cvs/src/sys/uvm/uvm_fault.c,v
> > retrieving revision 1.115
> > diff -u -p -r1.115 uvm_fault.c
> > --- uvm/uvm_fault.c 16 Feb 2021 09:10:17 - 1.115
> > +++ uvm/uvm_fault.c 16 Feb 2021 10:13:58 -
> > @@ -598,10 +598,37 @@ uvm_fault(vm_map_t orig_map, vaddr_t vad
> > /* case 1: fault on an anon in our amap */
> > error = uvm_fault_upper(, , anons, fault_type);
> > } else {
> > - /* case 2: fault on backing object or zero fill */
> > - KERNEL_LOCK();
> > - error = uvm_fault_lower(, , pages, fault_type);
> > - KERNEL_UNLOCK();
> > + struct uvm_object *uobj = ufi.entry->object.uvm_obj;
> > +
> > + /*
> > +* if the desired page is not shadowed by the amap and
> > +* we have a backing object, then we check to see if
> > +* the backing object would prefer to handle the fault
> > +* itself (rather than letting us do it with the usual
> > +* pgo_get hook). the backing object signals this by
> > +* providing a pgo_fault routine.
> > +*/
> > + if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > + KERNEL_LOCK();
> > + error = uobj->pgops->pgo_fault(,
> > + flt.startva, pages, flt.npages,
> > + flt.centeridx, fault_type, flt.access_type,
> > + PGO_LOCKED);
> > + KERNEL_UNLOCK();
> > +
> > + if (error == VM_PAGER_OK)
> > + error = 0;
> > + else if (error == VM_PAGER_REFAULT)
> > + error = ERESTART;
> > + else
> > + error = EACCES;
> > + } else {
> > + /* case 2: fault on backing obj or zero fill */
> > + KERNEL_LOCK();
> > + error = uvm_fault_lower(, , pages,
> > + fault_type);
> > + KERNEL_UNLOCK();
> > + }
> > }
> > }
> >
> > @@ -1054,26 +1081,6 @@ uvm_fault_lower(struct uvm_faultinfo *uf
> > struct vm_anon *anon = NULL;
> > vaddr_t currva;
> > voff_t uoff;
> > -
> > - /*
> > -* if the desired page is not shadowed by the amap and we have a
> > -* backing object, then we check to see if the backing object would
> > -* prefer to handle the fault itself (rather than letting us do it
> > -* with the usual pgo_get hook). the backing object signals this by
> > -* providing a pgo_fault routine.
> > -*/
> > - if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> > - result = uobj->pgops->pgo_fault(ufi, flt->startva, pages,
> > - flt->npages, flt->centeridx, fault_type, flt->access_type,
> > - PGO_LOCKED);
> > -
> > - if (result == VM_PAGER_OK)
> > - return (0); /* pgo_fault did pmap enter */
> > - else if (result == VM_PAGER_REFAULT)
> > - return ERESTART;/* try again! */
> > - else
> > - return (EACCES);
> > - }
> >
> > /*
> > * now, if the desired page is not shadowed by the amap and we have
> >
>
>
Re: uvm_fault_lower refactoring
Martin Pieuchot [m...@openbsd.org] wrote: > On 16/02/21(Tue) 11:20, Martin Pieuchot wrote: > > Start by moving `pgo_fault' handler outside of uvm_fault_lower(). > > > > If a page has a backing object that prefer to handler to fault itself > > the locking will be different, so keep it under KERNEL_LOCK() for the > > moment and make it separate from the rest of uvm_fault_lower(). > > > > ok? > > Anyone? > It makes sense, and works on my workstation...
Re: uvm_fault_lower refactoring
On 16/02/21(Tue) 11:20, Martin Pieuchot wrote:
> Start by moving `pgo_fault' handler outside of uvm_fault_lower().
>
> If a page has a backing object that prefer to handler to fault itself
> the locking will be different, so keep it under KERNEL_LOCK() for the
> moment and make it separate from the rest of uvm_fault_lower().
>
> ok?
Anyone?
>
> Index: uvm/uvm_fault.c
> ===
> RCS file: /cvs/src/sys/uvm/uvm_fault.c,v
> retrieving revision 1.115
> diff -u -p -r1.115 uvm_fault.c
> --- uvm/uvm_fault.c 16 Feb 2021 09:10:17 - 1.115
> +++ uvm/uvm_fault.c 16 Feb 2021 10:13:58 -
> @@ -598,10 +598,37 @@ uvm_fault(vm_map_t orig_map, vaddr_t vad
> /* case 1: fault on an anon in our amap */
> error = uvm_fault_upper(, , anons, fault_type);
> } else {
> - /* case 2: fault on backing object or zero fill */
> - KERNEL_LOCK();
> - error = uvm_fault_lower(, , pages, fault_type);
> - KERNEL_UNLOCK();
> + struct uvm_object *uobj = ufi.entry->object.uvm_obj;
> +
> + /*
> + * if the desired page is not shadowed by the amap and
> + * we have a backing object, then we check to see if
> + * the backing object would prefer to handle the fault
> + * itself (rather than letting us do it with the usual
> + * pgo_get hook). the backing object signals this by
> + * providing a pgo_fault routine.
> + */
> + if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> + KERNEL_LOCK();
> + error = uobj->pgops->pgo_fault(,
> + flt.startva, pages, flt.npages,
> + flt.centeridx, fault_type, flt.access_type,
> + PGO_LOCKED);
> + KERNEL_UNLOCK();
> +
> + if (error == VM_PAGER_OK)
> + error = 0;
> + else if (error == VM_PAGER_REFAULT)
> + error = ERESTART;
> + else
> + error = EACCES;
> + } else {
> + /* case 2: fault on backing obj or zero fill */
> + KERNEL_LOCK();
> + error = uvm_fault_lower(, , pages,
> + fault_type);
> + KERNEL_UNLOCK();
> + }
> }
> }
>
> @@ -1054,26 +1081,6 @@ uvm_fault_lower(struct uvm_faultinfo *uf
> struct vm_anon *anon = NULL;
> vaddr_t currva;
> voff_t uoff;
> -
> - /*
> - * if the desired page is not shadowed by the amap and we have a
> - * backing object, then we check to see if the backing object would
> - * prefer to handle the fault itself (rather than letting us do it
> - * with the usual pgo_get hook). the backing object signals this by
> - * providing a pgo_fault routine.
> - */
> - if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
> - result = uobj->pgops->pgo_fault(ufi, flt->startva, pages,
> - flt->npages, flt->centeridx, fault_type, flt->access_type,
> - PGO_LOCKED);
> -
> - if (result == VM_PAGER_OK)
> - return (0); /* pgo_fault did pmap enter */
> - else if (result == VM_PAGER_REFAULT)
> - return ERESTART;/* try again! */
> - else
> - return (EACCES);
> - }
>
> /*
>* now, if the desired page is not shadowed by the amap and we have
>
uvm_fault_lower refactoring
Start by moving `pgo_fault' handler outside of uvm_fault_lower().
If a page has a backing object that prefer to handler to fault itself
the locking will be different, so keep it under KERNEL_LOCK() for the
moment and make it separate from the rest of uvm_fault_lower().
ok?
Index: uvm/uvm_fault.c
===
RCS file: /cvs/src/sys/uvm/uvm_fault.c,v
retrieving revision 1.115
diff -u -p -r1.115 uvm_fault.c
--- uvm/uvm_fault.c 16 Feb 2021 09:10:17 - 1.115
+++ uvm/uvm_fault.c 16 Feb 2021 10:13:58 -
@@ -598,10 +598,37 @@ uvm_fault(vm_map_t orig_map, vaddr_t vad
/* case 1: fault on an anon in our amap */
error = uvm_fault_upper(, , anons, fault_type);
} else {
- /* case 2: fault on backing object or zero fill */
- KERNEL_LOCK();
- error = uvm_fault_lower(, , pages, fault_type);
- KERNEL_UNLOCK();
+ struct uvm_object *uobj = ufi.entry->object.uvm_obj;
+
+ /*
+* if the desired page is not shadowed by the amap and
+* we have a backing object, then we check to see if
+* the backing object would prefer to handle the fault
+* itself (rather than letting us do it with the usual
+* pgo_get hook). the backing object signals this by
+* providing a pgo_fault routine.
+*/
+ if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
+ KERNEL_LOCK();
+ error = uobj->pgops->pgo_fault(,
+ flt.startva, pages, flt.npages,
+ flt.centeridx, fault_type, flt.access_type,
+ PGO_LOCKED);
+ KERNEL_UNLOCK();
+
+ if (error == VM_PAGER_OK)
+ error = 0;
+ else if (error == VM_PAGER_REFAULT)
+ error = ERESTART;
+ else
+ error = EACCES;
+ } else {
+ /* case 2: fault on backing obj or zero fill */
+ KERNEL_LOCK();
+ error = uvm_fault_lower(, , pages,
+ fault_type);
+ KERNEL_UNLOCK();
+ }
}
}
@@ -1054,26 +1081,6 @@ uvm_fault_lower(struct uvm_faultinfo *uf
struct vm_anon *anon = NULL;
vaddr_t currva;
voff_t uoff;
-
- /*
-* if the desired page is not shadowed by the amap and we have a
-* backing object, then we check to see if the backing object would
-* prefer to handle the fault itself (rather than letting us do it
-* with the usual pgo_get hook). the backing object signals this by
-* providing a pgo_fault routine.
-*/
- if (uobj != NULL && uobj->pgops->pgo_fault != NULL) {
- result = uobj->pgops->pgo_fault(ufi, flt->startva, pages,
- flt->npages, flt->centeridx, fault_type, flt->access_type,
- PGO_LOCKED);
-
- if (result == VM_PAGER_OK)
- return (0); /* pgo_fault did pmap enter */
- else if (result == VM_PAGER_REFAULT)
- return ERESTART;/* try again! */
- else
- return (EACCES);
- }
/*
* now, if the desired page is not shadowed by the amap and we have
