svn commit: r313186 - head/sys/vm
Alan Cox
alc at FreeBSD.org
Sat Feb 4 05:23:13 UTC 2017
Author: alc
Date: Sat Feb 4 05:23:10 2017
New Revision: 313186
URL: https://svnweb.freebsd.org/changeset/base/313186
Log:
Over the years, the code and comments in vm_page_startup() have diverged in
one respect. When determining how many page structures to allocate,
contrary to what the comments say, the code does not account for the
overhead of a page structure per page of physical memory. This revision
changes the code to match the comments.
Reviewed by: kib, markj
MFC after: 6 weeks
Differential Revision: https://reviews.freebsd.org/D9081
Modified:
head/sys/vm/vm_page.c
Modified: head/sys/vm/vm_page.c
==============================================================================
--- head/sys/vm/vm_page.c Sat Feb 4 05:09:47 2017 (r313185)
+++ head/sys/vm/vm_page.c Sat Feb 4 05:23:10 2017 (r313186)
@@ -421,17 +421,16 @@ vm_page_domain_init(struct vm_domain *vm
/*
* vm_page_startup:
*
- * Initializes the resident memory module.
- *
- * Allocates memory for the page cells, and
- * for the object/offset-to-page hash table headers.
- * Each page cell is initialized and placed on the free list.
+ * Initializes the resident memory module. Allocates physical memory for
+ * bootstrapping UMA and some data structures that are used to manage
+ * physical pages. Initializes these structures, and populates the free
+ * page queues.
*/
vm_offset_t
vm_page_startup(vm_offset_t vaddr)
{
vm_offset_t mapped;
- vm_paddr_t page_range;
+ vm_paddr_t high_avail, low_avail, page_range, size;
vm_paddr_t new_end;
int i;
vm_paddr_t pa;
@@ -439,7 +438,6 @@ vm_page_startup(vm_offset_t vaddr)
char *list, *listend;
vm_paddr_t end;
vm_paddr_t biggestsize;
- vm_paddr_t low_water, high_water;
int biggestone;
int pages_per_zone;
@@ -451,27 +449,12 @@ vm_page_startup(vm_offset_t vaddr)
phys_avail[i] = round_page(phys_avail[i]);
phys_avail[i + 1] = trunc_page(phys_avail[i + 1]);
}
-
- low_water = phys_avail[0];
- high_water = phys_avail[1];
-
- for (i = 0; i < vm_phys_nsegs; i++) {
- if (vm_phys_segs[i].start < low_water)
- low_water = vm_phys_segs[i].start;
- if (vm_phys_segs[i].end > high_water)
- high_water = vm_phys_segs[i].end;
- }
for (i = 0; phys_avail[i + 1]; i += 2) {
- vm_paddr_t size = phys_avail[i + 1] - phys_avail[i];
-
+ size = phys_avail[i + 1] - phys_avail[i];
if (size > biggestsize) {
biggestone = i;
biggestsize = size;
}
- if (phys_avail[i] < low_water)
- low_water = phys_avail[i];
- if (phys_avail[i + 1] > high_water)
- high_water = phys_avail[i + 1];
}
end = phys_avail[biggestone+1];
@@ -486,7 +469,7 @@ vm_page_startup(vm_offset_t vaddr)
vm_page_domain_init(&vm_dom[i]);
/*
- * Almost all of the pages needed for boot strapping UMA are used
+ * Almost all of the pages needed for bootstrapping UMA are used
* for zone structures, so if the number of CPUs results in those
* structures taking more than one page each, we set aside more pages
* in proportion to the zone structure size.
@@ -537,6 +520,16 @@ vm_page_startup(vm_offset_t vaddr)
new_end + vm_page_dump_size, VM_PROT_READ | VM_PROT_WRITE);
bzero((void *)vm_page_dump, vm_page_dump_size);
#endif
+#if defined(__aarch64__) || defined(__amd64__) || defined(__mips__)
+ /*
+ * Include the UMA bootstrap pages and vm_page_dump in a crash dump.
+ * When pmap_map() uses the direct map, they are not automatically
+ * included.
+ */
+ for (pa = new_end; pa < end; pa += PAGE_SIZE)
+ dump_add_page(pa);
+#endif
+ phys_avail[biggestone + 1] = new_end;
#ifdef __amd64__
/*
* Request that the physical pages underlying the message buffer be
@@ -552,20 +545,48 @@ vm_page_startup(vm_offset_t vaddr)
#endif
/*
* Compute the number of pages of memory that will be available for
- * use (taking into account the overhead of a page structure per
- * page).
+ * use, taking into account the overhead of a page structure per page.
+ * In other words, solve
+ * "available physical memory" - round_page(page_range *
+ * sizeof(struct vm_page)) = page_range * PAGE_SIZE
+ * for page_range.
*/
- first_page = low_water / PAGE_SIZE;
-#ifdef VM_PHYSSEG_SPARSE
- page_range = 0;
+ low_avail = phys_avail[0];
+ high_avail = phys_avail[1];
for (i = 0; i < vm_phys_nsegs; i++) {
- page_range += atop(vm_phys_segs[i].end -
- vm_phys_segs[i].start);
+ if (vm_phys_segs[i].start < low_avail)
+ low_avail = vm_phys_segs[i].start;
+ if (vm_phys_segs[i].end > high_avail)
+ high_avail = vm_phys_segs[i].end;
+ }
+ /* Skip the first chunk. It is already accounted for. */
+ for (i = 2; phys_avail[i + 1] != 0; i += 2) {
+ if (phys_avail[i] < low_avail)
+ low_avail = phys_avail[i];
+ if (phys_avail[i + 1] > high_avail)
+ high_avail = phys_avail[i + 1];
}
+ first_page = low_avail / PAGE_SIZE;
+#ifdef VM_PHYSSEG_SPARSE
+ size = 0;
+ for (i = 0; i < vm_phys_nsegs; i++)
+ size += vm_phys_segs[i].end - vm_phys_segs[i].start;
for (i = 0; phys_avail[i + 1] != 0; i += 2)
- page_range += atop(phys_avail[i + 1] - phys_avail[i]);
+ size += phys_avail[i + 1] - phys_avail[i];
+ page_range = size / (PAGE_SIZE + sizeof(struct vm_page));
#elif defined(VM_PHYSSEG_DENSE)
- page_range = high_water / PAGE_SIZE - first_page;
+ /*
+ * In the VM_PHYSSEG_DENSE case, the number of pages can account for
+ * the overhead of a page structure per page only if vm_page_array is
+ * allocated from the last physical memory chunk. Otherwise, we must
+ * allocate page structures representing the physical memory
+ * underlying vm_page_array, even though they will not be used.
+ */
+ if (new_end == high_avail)
+ page_range = (high_avail - low_avail) / (PAGE_SIZE +
+ sizeof(struct vm_page));
+ else
+ page_range = high_avail / PAGE_SIZE - first_page;
#else
#error "Either VM_PHYSSEG_DENSE or VM_PHYSSEG_SPARSE must be defined."
#endif
@@ -573,12 +594,13 @@ vm_page_startup(vm_offset_t vaddr)
/*
* Reserve an unmapped guard page to trap access to vm_page_array[-1].
+ * However, because this page is allocated from KVM, out-of-bounds
+ * accesses using the direct map will not be trapped.
*/
vaddr += PAGE_SIZE;
/*
- * Initialize the mem entry structures now, and put them in the free
- * queue.
+ * Allocate physical memory for the page structures, and map it.
*/
new_end = trunc_page(end - page_range * sizeof(struct vm_page));
mapped = pmap_map(&vaddr, new_end, end,
@@ -586,19 +608,18 @@ vm_page_startup(vm_offset_t vaddr)
vm_page_array = (vm_page_t) mapped;
#if VM_NRESERVLEVEL > 0
/*
- * Allocate memory for the reservation management system's data
- * structures.
+ * Allocate physical memory for the reservation management system's
+ * data structures, and map it.
*/
- new_end = vm_reserv_startup(&vaddr, new_end, high_water);
+ if (high_avail == end)
+ high_avail = new_end;
+ new_end = vm_reserv_startup(&vaddr, new_end, high_avail);
#endif
#if defined(__aarch64__) || defined(__amd64__) || defined(__mips__)
/*
- * pmap_map on arm64, amd64, and mips can come out of the direct-map,
- * not kvm like i386, so the pages must be tracked for a crashdump to
- * include this data. This includes the vm_page_array and the early
- * UMA bootstrap pages.
+ * Include vm_page_array and vm_reserv_array in a crash dump.
*/
- for (pa = new_end; pa < phys_avail[biggestone + 1]; pa += PAGE_SIZE)
+ for (pa = new_end; pa < end; pa += PAGE_SIZE)
dump_add_page(pa);
#endif
phys_avail[biggestone + 1] = new_end;
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