On Tue, Mar 26, 2019 at 09:45:22PM +0800, Baoquan He wrote: > On 03/26/19 at 11:17am, Michal Hocko wrote: > > On Tue 26-03-19 18:08:17, Baoquan He wrote: > > > On 03/26/19 at 10:29am, Michal Hocko wrote: > > > > 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. > > > > > > In !VMEMMAP case, it truly does simple allocation directly. surely > > > usemap which size is 32 is smaller. So it doesn't matter that much who's > > > ahead or who's behind. However, this benefit a little in VMEMMAP case. > > > > How does it help there? The failure should be even much less probable > > there because we simply fall back to a small 4kB pages and those > > essentially never fail. > > OK, I am fine to drop it. Or only put the section existence checking > earlier to avoid unnecessary usemap/memmap allocation? > > > From 7594b86ebf5d6fcc8146eca8fc5625f1961a15b1 Mon Sep 17 00:00:00 2001 > From: Baoquan He <b...@redhat.com> > Date: Tue, 26 Mar 2019 18:48:39 +0800 > Subject: [PATCH] mm/sparse: Check section's existence earlier in > sparse_add_one_section() > > No need to allocate usemap and memmap if section has been present. > And can clean up the handling on failure. > > Signed-off-by: Baoquan He <b...@redhat.com> > --- > mm/sparse.c | 21 ++++++++------------- > 1 file changed, 8 insertions(+), 13 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 363f9d31b511..f564b531e0f7 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -714,7 +714,13 @@ 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; > + > + ms = __pfn_to_section(start_pfn); > + if (ms->section_mem_map & SECTION_MARKED_PRESENT) { > + ret = -EEXIST; > + goto out;
return -EEXIST; ? > + } > + > memmap = kmalloc_section_memmap(section_nr, nid, altmap); > if (!memmap) > return -ENOMEM; > @@ -724,12 +730,6 @@ int __meminit sparse_add_one_section(int nid, unsigned > long start_pfn, > return -ENOMEM; > } > > - ms = __pfn_to_section(start_pfn); > - if (ms->section_mem_map & SECTION_MARKED_PRESENT) { > - ret = -EEXIST; > - goto out; > - } > - > /* > * Poison uninitialized struct pages in order to catch invalid flags > * combinations. > @@ -739,12 +739,7 @@ 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 > -- Sincerely yours, Mike.