The patch titled
SLUB: Explain the 64k limits
has been removed from the -mm tree. Its filename was
slub-core-explain-the-64k-limits.patch
This patch was dropped because it was folded into slub-core.patch
------------------------------------------------------
Subject: SLUB: Explain the 64k limits
From: Christoph Lameter <clameter@xxxxxxx>
Note that these limits could now be removed since we no longer use
page->private for compound pages. But I think this is fine for now.
Signed-off-by: Christoph Lameter <clameter@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 22 +++++++++++++++++++++-
1 files changed, 21 insertions(+), 1 deletion(-)
diff -puN mm/slub.c~slub-core-explain-the-64k-limits mm/slub.c
--- a/mm/slub.c~slub-core-explain-the-64k-limits
+++ a/mm/slub.c
@@ -1571,6 +1571,12 @@ static int calculate_sizes(struct kmem_c
return 0;
s->objects = (PAGE_SIZE << s->order) / size;
+
+ /*
+ * Verify that the number of objects is within permitted limits.
+ * The page->inuse field is only 16 bit wide! So we cannot have
+ * more than 64k objects per slab.
+ */
if (!s->objects || s->objects > 65535)
return 0;
return 1;
@@ -1593,9 +1599,23 @@ static int kmem_cache_open(struct kmem_c
BUG_ON(flags & SLUB_UNIMPLEMENTED);
- if (s->size >= 65535 * sizeof(void *))
+ /*
+ * The page->offset field is only 16 bit wide. This is an offset
+ * in units of words from the beginning of an object. If the slab
+ * size is bigger then we cannot move the free pointer behind the
+ * object anymore.
+ *
+ * On 32 bit platforms the limit is 256k. On 64bit platforms
+ * the limit is 512k.
+ *
+ * Debugging or ctor/dtors may create a need to move the free
+ * pointer. Fail if this happens.
+ */
+ if (s->size >= 65535 * sizeof(void *)) {
BUG_ON(flags & (SLAB_RED_ZONE | SLAB_POISON |
SLAB_STORE_USER | SLAB_DESTROY_BY_RCU));
+ BUG_ON(ctor || dtor);
+ }
else
/*
* Enable debugging if selected on the kernel commandline.
_
Patches currently in -mm which might be from clameter@xxxxxxx are
slab-introduce-krealloc.patch
ia64-sn-xpc-convert-to-use-kthread-api-fix.patch
add-apply_to_page_range-which-applies-a-function-to-a-pte-range.patch
safer-nr_node_ids-and-nr_node_ids-determination-and-initial.patch
use-zvc-counters-to-establish-exact-size-of-dirtyable-pages.patch
slab-ensure-cache_alloc_refill-terminates.patch
smaps-extract-pmd-walker-from-smaps-code.patch
smaps-add-pages-referenced-count-to-smaps.patch
smaps-add-clear_refs-file-to-clear-reference.patch
slab-use-num_possible_cpus-in-enable_cpucache.patch
extend-print_symbol-capability.patch
i386-use-page-allocator-to-allocate-thread_info-structure.patch
slub-core.patch
slub-core-explain-the-64k-limits.patch
slub-core-explain-sizing-of-slabs-in-detail.patch
slub-core-explain-sizing-of-slabs-in-detail-fix.patch
slub-core-add-checks-for-interrupts-disabled.patch
slub-core-use-__print_symbol-instead-of-kallsyms_lookup.patch
slub-core-missing-inlines-and-statics.patch
slub-fix-cpu-slab-flushing-behavior-so-that-counters-match.patch
slub-extract-finish_bootstrap-function-for-clean-sysfs-boot.patch
slub-core-fix-kmem_cache_destroy.patch
slub-core-fix-validation.patch
slub-core-add-after-object-padding.patch
slub-core-resiliency-fixups.patch
slub-core-resiliency-fixups-fix.patch
slub-core-resiliency-test.patch
slub-core-update-cpu-after-new_slab.patch
slub-core-fix-sysfs-directory-handling.patch
slub-core-conform-more-to-slabs-slab_hwcache_align-behavior.patch
slub-core-reduce-the-order-of-allocations-to-avoid-fragmentation.patch
make-page-private-usable-in-compound-pages-v1.patch
make-page-private-usable-in-compound-pages-v1-hugetlb-fix.patch
optimize-compound_head-by-avoiding-a-shared-page.patch
add-virt_to_head_page-and-consolidate-code-in-slab-and-slub.patch
slub-fix-object-tracking.patch
slub-enable-tracking-of-full-slabs.patch
slub-enable-tracking-of-full-slabs-fix.patch
slub-enable-tracking-of-full-slabs-add-checks-for-interrupts-disabled.patch
slub-validation-of-slabs-metadata-and-guard-zones.patch
slub-validation-of-slabs-metadata-and-guard-zones-fix-pageerror-checks-during-validation.patch
slub-validation-of-slabs-metadata-and-guard-zones-remove-duplicate-vm_bug_on.patch
slub-add-min_partial.patch
slub-add-ability-to-list-alloc--free-callers-per-slab.patch
slub-add-ability-to-list-alloc--free-callers-per-slab-tidy.patch
slub-free-slabs-and-sort-partial-slab-lists-in-kmem_cache_shrink.patch
slub-remove-object-activities-out-of-checking-functions.patch
slub-user-documentation.patch
slub-user-documentation-fix.patch
slub-add-slabinfo-tool.patch
slub-add-slabinfo-tool-update-slabinfoc.patch
slub-major-slabinfo-update.patch
slub-exploit-page-mobility-to-increase-allocation-order.patch
slub-mm-only-make-slub-the-default-slab-allocator.patch
quicklists-for-page-table-pages.patch
quicklists-for-page-table-pages-avoid-useless-virt_to_page-conversion.patch
quicklists-for-page-table-pages-avoid-useless-virt_to_page-conversion-fix.patch
quicklist-support-for-ia64.patch
quicklist-support-for-x86_64.patch
quicklist-support-for-sparc64.patch
slab-allocators-remove-obsolete-slab_must_hwcache_align.patch
kmem_cache-simplify-slab-cache-creation.patch
slab-allocators-remove-slab_debug_initial-flag.patch
slab-allocators-remove-slab_debug_initial-flag-locks-fix.patch
slab-allocators-remove-multiple-alignment-specifications.patch
slab-allocators-remove-slab_ctor_atomic.patch
fault-injection-fix-failslab-with-config_numa.patch
mm-fix-handling-of-panic_on_oom-when-cpusets-are-in-use.patch
slub-i386-support.patch
slab-shutdown-cache_reaper-when-cpu-goes-down.patch
mm-implement-swap-prefetching.patch
revoke-core-code-slab-allocators-remove-slab_debug_initial-flag-revoke.patch
readahead-state-based-method-aging-accounting.patch
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