| Message ID | 20191119092642.31799-1-mhocko@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm, sparse: do not waste pre allocated memmap space | expand |
On 19.11.19 10:26, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > 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 > Reported-and-debugged-by: Vincent Whitchurch <vincent.whitchurch@axis.com> > Fixes: 35fd1eb1e821 ("mm/sparse: abstract sparse buffer allocations") > Signed-off-by: Michal Hocko <mhocko@suse.com> > --- > mm/sparse.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index f6891c1992b1..079f3e3c4cab 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(size, > - PAGE_SIZE, addr, > + map = memblock_alloc_try_nid(size, size, addr, > MEMBLOCK_ALLOC_ACCESSIBLE, nid); > if (!map) > panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%pa\n", > @@ -482,8 +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()? */ > + /* > + * 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, PAGE_SIZE, > + memblock_alloc_try_nid_raw(size, section_map_size(), > addr, > MEMBLOCK_ALLOC_ACCESSIBLE, nid); Wow, that alignment/layout gives me nightmares ^ None of your business, though :) > sparsemap_buf_end = sparsemap_buf + size; > Acked-by: David Hildenbrand <david@redhat.com>
On Tue, 19 Nov 2019 11:03:58 +0100 David Hildenbrand <david@redhat.com> wrote: > > @@ -482,8 +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()? */ > > + /* > > + * 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, PAGE_SIZE, > > + memblock_alloc_try_nid_raw(size, section_map_size(), > > addr, > > MEMBLOCK_ALLOC_ACCESSIBLE, nid); > > Wow, that alignment/layout gives me nightmares ^ > > None of your business, though :) We're allowed to change it ;) --- a/mm/sparse.c~mm-sparse-do-not-waste-pre-allocated-memmap-space-fix +++ a/mm/sparse.c @@ -486,10 +486,8 @@ static void __init sparse_buffer_init(un * 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 = memblock_alloc_try_nid_raw(size, section_map_size(), + addr, MEMBLOCK_ALLOC_ACCESSIBLE, nid); sparsemap_buf_end = sparsemap_buf + size; }
On Tue 19-11-19 14:10:47, Andrew Morton wrote: > On Tue, 19 Nov 2019 11:03:58 +0100 David Hildenbrand <david@redhat.com> wrote: > > > > @@ -482,8 +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()? */ > > > + /* > > > + * 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, PAGE_SIZE, > > > + memblock_alloc_try_nid_raw(size, section_map_size(), > > > addr, > > > MEMBLOCK_ALLOC_ACCESSIBLE, nid); > > > > Wow, that alignment/layout gives me nightmares ^ > > > > None of your business, though :) > > We're allowed to change it ;) > > --- a/mm/sparse.c~mm-sparse-do-not-waste-pre-allocated-memmap-space-fix > +++ a/mm/sparse.c > @@ -486,10 +486,8 @@ static void __init sparse_buffer_init(un > * 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 = memblock_alloc_try_nid_raw(size, section_map_size(), > + addr, MEMBLOCK_ALLOC_ACCESSIBLE, nid); > sparsemap_buf_end = sparsemap_buf + size; > } I didn't bother mostly because the creative code layout made the intention of the patch more obvious. But if it saves from nightmares then why not.
diff --git a/mm/sparse.c b/mm/sparse.c index f6891c1992b1..079f3e3c4cab 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(size, - PAGE_SIZE, addr, + map = memblock_alloc_try_nid(size, size, addr, MEMBLOCK_ALLOC_ACCESSIBLE, nid); if (!map) panic("%s: Failed to allocate %lu bytes align=0x%lx nid=%d from=%pa\n", @@ -482,8 +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()? */ + /* + * 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, PAGE_SIZE, + memblock_alloc_try_nid_raw(size, section_map_size(), addr, MEMBLOCK_ALLOC_ACCESSIBLE, nid); sparsemap_buf_end = sparsemap_buf + size;