svn commit: r187701 - user/alc/zerocopy/sys/vm

[Jeff Roberson]

On Mon, 26 Jan 2009, Alan Cox wrote:

> Author: alc
> Date: Mon Jan 26 00:52:09 2009
> New Revision: 187701
> URL: http://svn.freebsd.org/changeset/base/187701
>
> Log:
>  Retire the page-based copy-on-write mechanism.
Hey if we're doing this there are some mbuf fields I could axe too. :-)

This isn't productive for anyone anyway eh?  I've done page-flipping to 
kernel for nfs and custom protocols but to userland it just doesn't make 
sense without an api to support it.

Thanks,
Jeff


>
> Modified:
>  user/alc/zerocopy/sys/vm/vm_fault.c
>  user/alc/zerocopy/sys/vm/vm_page.c
>  user/alc/zerocopy/sys/vm/vm_page.h
>
> Modified: user/alc/zerocopy/sys/vm/vm_fault.c
> ==============================================================================
> --- user/alc/zerocopy/sys/vm/vm_fault.c	Sun Jan 25 23:08:47 2009	(r187700)
> +++ user/alc/zerocopy/sys/vm/vm_fault.c	Mon Jan 26 00:52:09 2009	(r187701)
> @@ -330,25 +330,6 @@ RetryFault:;
> 		 */
> 		fs.m = vm_page_lookup(fs.object, fs.pindex);
> 		if (fs.m != NULL) {
> -			/*
> -			 * check for page-based copy on write.
> -			 * We check fs.object == fs.first_object so
> -			 * as to ensure the legacy COW mechanism is
> -			 * used when the page in question is part of
> -			 * a shadow object.  Otherwise, vm_page_cowfault()
> -			 * removes the page from the backing object,
> -			 * which is not what we want.
> -			 */
> -			vm_page_lock_queues();
> -			if ((fs.m->cow) &&
> -			    (fault_type & VM_PROT_WRITE) &&
> -			    (fs.object == fs.first_object)) {
> -				vm_page_cowfault(fs.m);
> -				vm_page_unlock_queues();
> -				unlock_and_deallocate(&fs);
> -				goto RetryFault;
> -			}
> -
> 			/*
> 			 * Wait/Retry if the page is busy.  We have to do this
> 			 * if the page is busy via either VPO_BUSY or
> @@ -366,7 +347,6 @@ RetryFault:;
> 			 * to pmap it.
> 			 */
> 			if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) {
> -				vm_page_unlock_queues();
> 				VM_OBJECT_UNLOCK(fs.object);
> 				if (fs.object != fs.first_object) {
> 					VM_OBJECT_LOCK(fs.first_object);
> @@ -398,6 +378,7 @@ RetryFault:;
> 				vm_object_deallocate(fs.first_object);
> 				goto RetryFault;
> 			}
> +			vm_page_lock_queues();
> 			vm_pageq_remove(fs.m);
> 			vm_page_unlock_queues();
>
>
> Modified: user/alc/zerocopy/sys/vm/vm_page.c
> ==============================================================================
> --- user/alc/zerocopy/sys/vm/vm_page.c	Sun Jan 25 23:08:47 2009	(r187700)
> +++ user/alc/zerocopy/sys/vm/vm_page.c	Mon Jan 26 00:52:09 2009	(r187701)
> @@ -2033,98 +2033,6 @@ vm_page_test_dirty(vm_page_t m)
> 	}
> }
>
> -int so_zerocp_fullpage = 0;
> -
> -/*
> - *	Replace the given page with a copy.  The copied page assumes
> - *	the portion of the given page's "wire_count" that is not the
> - *	responsibility of this copy-on-write mechanism.
> - *
> - *	The object containing the given page must have a non-zero
> - *	paging-in-progress count and be locked.
> - */
> -void
> -vm_page_cowfault(vm_page_t m)
> -{
> -	vm_page_t mnew;
> -	vm_object_t object;
> -	vm_pindex_t pindex;
> -
> -	object = m->object;
> -	VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
> -	KASSERT(object->paging_in_progress != 0,
> -	    ("vm_page_cowfault: object %p's paging-in-progress count is zero.",
> -	    object));
> -	pindex = m->pindex;
> -
> - retry_alloc:
> -	pmap_remove_all(m);
> -	vm_page_remove(m);
> -	mnew = vm_page_alloc(object, pindex, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY);
> -	if (mnew == NULL) {
> -		vm_page_insert(m, object, pindex);
> -		vm_page_unlock_queues();
> -		VM_OBJECT_UNLOCK(object);
> -		VM_WAIT;
> -		VM_OBJECT_LOCK(object);
> -		if (m == vm_page_lookup(object, pindex)) {
> -			vm_page_lock_queues();
> -			goto retry_alloc;
> -		} else {
> -			/*
> -			 * Page disappeared during the wait.
> -			 */
> -			vm_page_lock_queues();
> -			return;
> -		}
> -	}
> -
> -	if (m->cow == 0) {
> -		/*
> -		 * check to see if we raced with an xmit complete when
> -		 * waiting to allocate a page.  If so, put things back
> -		 * the way they were
> -		 */
> -		vm_page_free(mnew);
> -		vm_page_insert(m, object, pindex);
> -	} else { /* clear COW & copy page */
> -		if (!so_zerocp_fullpage)
> -			pmap_copy_page(m, mnew);
> -		mnew->valid = VM_PAGE_BITS_ALL;
> -		vm_page_dirty(mnew);
> -		mnew->wire_count = m->wire_count - m->cow;
> -		m->wire_count = m->cow;
> -	}
> -}
> -
> -void
> -vm_page_cowclear(vm_page_t m)
> -{
> -
> -	mtx_assert(&vm_page_queue_mtx, MA_OWNED);
> -	if (m->cow) {
> -		m->cow--;
> -		/*
> -		 * let vm_fault add back write permission  lazily
> -		 */
> -	}
> -	/*
> -	 *  sf_buf_free() will free the page, so we needn't do it here
> -	 */
> -}
> -
> -int
> -vm_page_cowsetup(vm_page_t m)
> -{
> -
> -	mtx_assert(&vm_page_queue_mtx, MA_OWNED);
> -	if (m->cow == USHRT_MAX - 1)
> -		return (EBUSY);
> -	m->cow++;
> -	pmap_remove_write(m);
> -	return (0);
> -}
> -
> #include "opt_ddb.h"
> #ifdef DDB
> #include <sys/kernel.h>
>
> Modified: user/alc/zerocopy/sys/vm/vm_page.h
> ==============================================================================
> --- user/alc/zerocopy/sys/vm/vm_page.h	Sun Jan 25 23:08:47 2009	(r187700)
> +++ user/alc/zerocopy/sys/vm/vm_page.h	Mon Jan 26 00:52:09 2009	(r187701)
> @@ -115,7 +115,6 @@ struct vm_page {
> 	u_short	flags;			/* see below */
> 	uint8_t	order;			/* index of the buddy queue */
> 	uint8_t pool;
> -	u_short cow;			/* page cow mapping count */
> 	u_int wire_count;		/* wired down maps refs (P) */
> 	short hold_count;		/* page hold count */
> 	u_short oflags;			/* page flags (O) */
> @@ -335,9 +334,6 @@ int vm_page_bits (int, int);
> void vm_page_zero_invalid(vm_page_t m, boolean_t setvalid);
> void vm_page_free_toq(vm_page_t m);
> void vm_page_zero_idle_wakeup(void);
> -void vm_page_cowfault (vm_page_t);
> -int vm_page_cowsetup(vm_page_t);
> -void vm_page_cowclear (vm_page_t);
>
> /*
>  *	vm_page_sleep_if_busy:
>