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Message-Id: <20211115193725.737539-2-zi.yan@sent.com>
Date: Mon, 15 Nov 2021 14:37:22 -0500
From: Zi Yan <zi.yan@...t.com>
To: David Hildenbrand <david@...hat.com>, linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
Michael Ellerman <mpe@...erman.id.au>,
Christoph Hellwig <hch@....de>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Robin Murphy <robin.murphy@....com>,
linuxppc-dev@...ts.ozlabs.org,
virtualization@...ts.linux-foundation.org,
iommu@...ts.linux-foundation.org, Zi Yan <ziy@...dia.com>
Subject: [RFC PATCH 1/3] mm: cma: alloc_contig_range: use pageblock_order as the single alignment.
From: Zi Yan <ziy@...dia.com>
Pages are grouped in unit of pageblock_order for mobility. cma and
alloc_contig_range() uses pageblock for isolation and migration, so
aligning PFNs to pageblock_order is necessary. But the PFNs used in cma
and alloc_contig_range() were aligned to max(pageblock_order, MAX_ORDER-1).
This makes no difference than aligning only to pageblock_order, since
if pageblock_order > MAX_ORDER, the PFN is pageblock aligned,
otherwise, the PFN is still pageblock aligned. Drop MAX_ORDER alignment
requirement.
When commit 47118af076f6 ("mm: mmzone: MIGRATE_CMA migration type added")
introduced MIGRATE_CMA, __free_one_page() did not prevent merging
freepages on isolate pagelbock and normal pageblock, thus it required
max(pageblock_order, MAX_ORDER-1) alignment. __free_one_page() has
changed and does prevent such merges.
Signed-off-by: Zi Yan <ziy@...dia.com>
---
include/linux/mmzone.h | 5 +----
kernel/dma/contiguous.c | 2 +-
mm/cma.c | 6 ++----
mm/page_alloc.c | 12 +++++-------
4 files changed, 9 insertions(+), 16 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 58e744b78c2c..6c61aa41a779 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -54,10 +54,7 @@ enum migratetype {
*
* The way to use it is to change migratetype of a range of
* pageblocks to MIGRATE_CMA which can be done by
- * __free_pageblock_cma() function. What is important though
- * is that a range of pageblocks must be aligned to
- * MAX_ORDER_NR_PAGES should biggest page be bigger than
- * a single pageblock.
+ * __free_pageblock_cma() function.
*/
MIGRATE_CMA,
#endif
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index 3d63d91cba5c..ac35b14b0786 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -399,7 +399,7 @@ static const struct reserved_mem_ops rmem_cma_ops = {
static int __init rmem_cma_setup(struct reserved_mem *rmem)
{
- phys_addr_t align = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
+ phys_addr_t align = PAGE_SIZE << pageblock_order;
phys_addr_t mask = align - 1;
unsigned long node = rmem->fdt_node;
bool default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
diff --git a/mm/cma.c b/mm/cma.c
index bc9ca8f3c487..d171158bd418 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -180,8 +180,7 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
return -EINVAL;
/* ensure minimal alignment required by mm core */
- alignment = PAGE_SIZE <<
- max_t(unsigned long, MAX_ORDER - 1, pageblock_order);
+ alignment = PAGE_SIZE << pageblock_order;
/* alignment should be aligned with order_per_bit */
if (!IS_ALIGNED(alignment >> PAGE_SHIFT, 1 << order_per_bit))
@@ -268,8 +267,7 @@ int __init cma_declare_contiguous_nid(phys_addr_t base,
* migratetype page by page allocator's buddy algorithm. In the case,
* you couldn't get a contiguous memory, which is not what we want.
*/
- alignment = max(alignment, (phys_addr_t)PAGE_SIZE <<
- max_t(unsigned long, MAX_ORDER - 1, pageblock_order));
+ alignment = max(alignment, (phys_addr_t)PAGE_SIZE << pageblock_order);
if (fixed && base & (alignment - 1)) {
ret = -EINVAL;
pr_err("Region at %pa must be aligned to %pa bytes\n",
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c5952749ad40..5700f5502d59 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8922,14 +8922,12 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
#ifdef CONFIG_CONTIG_ALLOC
static unsigned long pfn_max_align_down(unsigned long pfn)
{
- return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
- pageblock_nr_pages) - 1);
+ return pfn & ~(pageblock_nr_pages - 1);
}
static unsigned long pfn_max_align_up(unsigned long pfn)
{
- return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
- pageblock_nr_pages));
+ return ALIGN(pfn, pageblock_nr_pages);
}
#if defined(CONFIG_DYNAMIC_DEBUG) || \
@@ -9022,8 +9020,8 @@ static int __alloc_contig_migrate_range(struct compact_control *cc,
* be either of the two.
* @gfp_mask: GFP mask to use during compaction
*
- * The PFN range does not have to be pageblock or MAX_ORDER_NR_PAGES
- * aligned. The PFN range must belong to a single zone.
+ * The PFN range does not have to be pageblock aligned. The PFN range must
+ * belong to a single zone.
*
* The first thing this routine does is attempt to MIGRATE_ISOLATE all
* pageblocks in the range. Once isolated, the pageblocks should not
@@ -9099,7 +9097,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
ret = 0;
/*
- * Pages from [start, end) are within a MAX_ORDER_NR_PAGES
+ * Pages from [start, end) are within a pageblock_nr_pages
* aligned blocks that are marked as MIGRATE_ISOLATE. What's
* more, all pages in [start, end) are free in page allocator.
* What we are going to do is to allocate all pages from
--
2.33.0
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