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authorMichal Hocko <mhocko@suse.com>2019-11-30 17:54:27 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-12-01 12:59:05 -0800
commit09dbcf422e9b791d2d43cad8c283d9bdaef019a9 (patch)
treea5028886e50f486626e2fa6414cc9b3b6deddbda /mm
parent030eab4f9ffb469344c10a46bc02c5149db0a2a9 (diff)
mm/sparse.c: do not waste pre allocated memmap space
Vincent has noticed [1] that there is something unusual with the memmap allocations going on on his platform : I noticed this because on my ARM64 platform, with 1 GiB of memory the : first [and only] section is allocated from the zeroing path while with : 2 GiB of memory the first 1 GiB section is allocated from the : non-zeroing path. The underlying problem is that although sparse_buffer_init allocates enough memory for all sections on the node sparse_buffer_alloc is not able to consume them due to mismatch in the expected allocation alignement. While sparse_buffer_init preallocation uses the PAGE_SIZE alignment the real memmap has to be aligned to section_map_size() this results in a wasted initial chunk of the preallocated memmap and unnecessary fallback allocation for a section. While we are at it also change __populate_section_memmap to align to the requested size because at least VMEMMAP has constrains to have memmap properly aligned. [1] http://lkml.kernel.org/r/20191030131122.8256-1-vincent.whitchurch@axis.com [akpm@linux-foundation.org: tweak layout, per David] Link: http://lkml.kernel.org/r/20191119092642.31799-1-mhocko@kernel.org Fixes: 35fd1eb1e821 ("mm/sparse: abstract sparse buffer allocations") Signed-off-by: Michal Hocko <mhocko@suse.com> Reported-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Debugged-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Oscar Salvador <OSalvador@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/sparse.c14
1 files changed, 8 insertions, 6 deletions
diff --git a/mm/sparse.c b/mm/sparse.c
index 163b4d59cf6c..8526d3bf1e4e 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -458,8 +458,7 @@ struct page __init *__populate_section_memmap(unsigned long pfn,
if (map)
return map;
- map = memblock_alloc_try_nid_raw(size,
- PAGE_SIZE, addr,
+ map = memblock_alloc_try_nid_raw(size, size, addr,
MEMBLOCK_ALLOC_ACCESSIBLE, nid);
if (!map)
panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%pa\n",
@@ -482,10 +481,13 @@ static void __init sparse_buffer_init(unsigned long size, int nid)
{
phys_addr_t addr = __pa(MAX_DMA_ADDRESS);
WARN_ON(sparsemap_buf); /* forgot to call sparse_buffer_fini()? */
- sparsemap_buf =
- memblock_alloc_try_nid_raw(size, PAGE_SIZE,
- addr,
- MEMBLOCK_ALLOC_ACCESSIBLE, nid);
+ /*
+ * Pre-allocated buffer is mainly used by __populate_section_memmap
+ * and we want it to be properly aligned to the section size - this is
+ * especially the case for VMEMMAP which maps memmap to PMDs
+ */
+ sparsemap_buf = memblock_alloc_try_nid_raw(size, section_map_size(),
+ addr, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
sparsemap_buf_end = sparsemap_buf + size;
}