git: e4bdb6857aea - main - vm_page: Handle VM_ALLOC_NORECLAIM in the contiguous page allocator

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=e4bdb6857aea466ce4af48c0bd05a214460fe313

commit e4bdb6857aea466ce4af48c0bd05a214460fe313
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2021-11-11 19:26:41 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2021-11-11 19:26:41 +0000

    vm_page: Handle VM_ALLOC_NORECLAIM in the contiguous page allocator
    
    We added _NORECLAIM to request that kmem_alloc_contig_pages() not spend
    time scanning physical memory for candidates to reclaim.  In some
    situations the scanning can induce large amounts of undesirable latency,
    and it's less important that the request be satisfied than it is that we
    not spend many milliseconds scanning.
    
    The problem extends to vm_reserv_reclaim_contig(), which unlike
    vm_reserv_reclaim() may have to scan the entire list of partially
    populated reservations.  Use VM_ALLOC_NORECLAIM to request that this
    scan not be executed.[1]
    
    As a side effect, this fixes a regression in 02fb0585e7b3 ("vm_page:
    Drop handling of VM_ALLOC_NOOBJ in vm_page_alloc_contig_domain()")
    where VM_ALLOC_CONTIG was not included in VPAC_FLAGS or VPANC_FLAGS even
    though it is not masked by kmem_alloc_contig_pages().[2]
    
    Reported by:    gallatin [1], glebius [2]
    Reviewed by:    alc, glebius, kib
    MFC after:      2 weeks
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D32899
---
 sys/vm/vm_kern.c |  4 ----
 sys/vm/vm_page.c | 16 ++++++++++++----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/sys/vm/vm_kern.c b/sys/vm/vm_kern.c
index 4ddeb3208260..669dc194759b 100644
--- a/sys/vm/vm_kern.c
+++ b/sys/vm/vm_kern.c
@@ -182,10 +182,6 @@ kmem_alloc_contig_pages(vm_object_t object, vm_pindex_t pindex, int domain,
 
 	VM_OBJECT_ASSERT_WLOCKED(object);
 
-	/* Disallow an invalid combination of flags. */
-	MPASS((pflags & (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM)) !=
-	    (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM));
-
 	wait = (pflags & VM_ALLOC_WAITOK) != 0;
 	reclaim = (pflags & VM_ALLOC_NORECLAIM) == 0;
 	pflags &= ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL);
diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index 76e9ba4db403..ac710bf43d08 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -2250,12 +2250,15 @@ vm_page_alloc_contig_domain(vm_object_t object, vm_pindex_t pindex, int domain,
 	vm_page_t m, m_ret, mpred;
 	u_int busy_lock, flags, oflags;
 
-#define	VPAC_FLAGS	VPA_FLAGS
+#define	VPAC_FLAGS	(VPA_FLAGS | VM_ALLOC_NORECLAIM)
 	KASSERT((req & ~VPAC_FLAGS) == 0,
 	    ("invalid request %#x", req));
 	KASSERT(((req & (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)) !=
 	    (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)),
 	    ("invalid request %#x", req));
+	KASSERT((req & (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM)) !=
+	    (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM),
+	    ("invalid request %#x", req));
 	VM_OBJECT_ASSERT_WLOCKED(object);
 	KASSERT((object->flags & OBJ_FICTITIOUS) == 0,
 	    ("vm_page_alloc_contig: object %p has fictitious pages",
@@ -2294,7 +2297,8 @@ again:
 		if (m_ret == NULL) {
 			vm_domain_freecnt_inc(vmd, npages);
 #if VM_NRESERVLEVEL > 0
-			if (vm_reserv_reclaim_contig(domain, npages, low,
+			if ((req & VM_ALLOC_NORECLAIM) == 0 &&
+			    vm_reserv_reclaim_contig(domain, npages, low,
 			    high, alignment, boundary))
 				goto again;
 #endif
@@ -2525,9 +2529,12 @@ vm_page_alloc_noobj_contig_domain(int domain, int req, u_long npages,
 	vm_page_t m, m_ret;
 	u_int flags;
 
-#define	VPANC_FLAGS	VPAN_FLAGS
+#define	VPANC_FLAGS	(VPAN_FLAGS | VM_ALLOC_NORECLAIM)
 	KASSERT((req & ~VPANC_FLAGS) == 0,
 	    ("invalid request %#x", req));
+	KASSERT((req & (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM)) !=
+	    (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM),
+	    ("invalid request %#x", req));
 	KASSERT(((req & (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)) !=
 	    (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)),
 	    ("invalid request %#x", req));
@@ -2547,7 +2554,8 @@ again:
 		if (m_ret == NULL) {
 			vm_domain_freecnt_inc(vmd, npages);
 #if VM_NRESERVLEVEL > 0
-			if (vm_reserv_reclaim_contig(domain, npages, low,
+			if ((req & VM_ALLOC_NORECLAIM) == 0 &&
+			    vm_reserv_reclaim_contig(domain, npages, low,
 			    high, alignment, boundary))
 				goto again;
 #endif