Date: Sun, 25 Jan 2009 17:24:04 -1000 (HST) From: Jeff Roberson <jroberson@jroberson.net> To: Alan Cox <alc@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-user@freebsd.org Subject: Re: svn commit: r187701 - user/alc/zerocopy/sys/vm Message-ID: <20090125172049.R983@desktop> In-Reply-To: <200901260052.n0Q0qAWN031905@svn.freebsd.org> References: <200901260052.n0Q0qAWN031905@svn.freebsd.org>
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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: >
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