On Tue 26-03-19 17:02:25, Baoquan He wrote: > Reorder the allocation of usemap and memmap since usemap allocation > is much simpler and easier. Otherwise hard work is done to make > memmap ready, then have to rollback just because of usemap allocation > failure.
Is this really worth it? I can see that !VMEMMAP is doing memmap size allocation which would be 2MB aka costly allocation but we do not do __GFP_RETRY_MAYFAIL so the allocator backs off early. > And also check if section is present earlier. Then don't bother to > allocate usemap and memmap if yes. Moving the check up makes some sense. > Signed-off-by: Baoquan He <b...@redhat.com> The patch is not incorrect but I am wondering whether it is really worth it for the current code base. Is it fixing anything real or it is a mere code shuffling to please an eye? > --- > v1->v2: > Do section existence checking earlier to further optimize code. > > mm/sparse.c | 29 +++++++++++------------------ > 1 file changed, 11 insertions(+), 18 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index b2111f996aa6..f4f34d69131e 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -714,20 +714,18 @@ int __meminit sparse_add_one_section(int nid, unsigned > long start_pfn, > ret = sparse_index_init(section_nr, nid); > if (ret < 0 && ret != -EEXIST) > return ret; > - ret = 0; > - memmap = kmalloc_section_memmap(section_nr, nid, altmap); > - if (!memmap) > - return -ENOMEM; > - usemap = __kmalloc_section_usemap(); > - if (!usemap) { > - __kfree_section_memmap(memmap, altmap); > - return -ENOMEM; > - } > > ms = __pfn_to_section(start_pfn); > - if (ms->section_mem_map & SECTION_MARKED_PRESENT) { > - ret = -EEXIST; > - goto out; > + if (ms->section_mem_map & SECTION_MARKED_PRESENT) > + return -EEXIST; > + > + usemap = __kmalloc_section_usemap(); > + if (!usemap) > + return -ENOMEM; > + memmap = kmalloc_section_memmap(section_nr, nid, altmap); > + if (!memmap) { > + kfree(usemap); > + return -ENOMEM; > } > > /* > @@ -739,12 +737,7 @@ int __meminit sparse_add_one_section(int nid, unsigned > long start_pfn, > section_mark_present(ms); > sparse_init_one_section(ms, section_nr, memmap, usemap); > > -out: > - if (ret < 0) { > - kfree(usemap); > - __kfree_section_memmap(memmap, altmap); > - } > - return ret; > + return 0; > } > > #ifdef CONFIG_MEMORY_HOTREMOVE > -- > 2.17.2 > -- Michal Hocko SUSE Labs