Messages in this thread Patch in this message | | | From | "Song Bao Hua (Barry Song)" <> | Subject | RE: [PATCH] mm/hugetlb: avoid hardcoding while checking if cma is reserved | Date | Mon, 6 Jul 2020 22:14:10 +0000 |
| |
> -----Original Message----- > From: Roman Gushchin [mailto:guro@fb.com] > Sent: Tuesday, July 7, 2020 9:48 AM > To: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com> > Cc: akpm@linux-foundation.org; linux-mm@kvack.org; > linux-kernel@vger.kernel.org; Linuxarm <linuxarm@huawei.com>; Mike > Kravetz <mike.kravetz@oracle.com>; Jonathan Cameron > <jonathan.cameron@huawei.com> > Subject: Re: [PATCH] mm/hugetlb: avoid hardcoding while checking if cma is > reserved > > On Mon, Jul 06, 2020 at 08:44:05PM +1200, Barry Song wrote: > > Hello, Barry! > > > hugetlb_cma[0] can be NULL due to various reasons, for example, node0 has > > no memory. Thus, NULL hugetlb_cma[0] doesn't necessarily mean cma is not > > enabled. gigantic pages might have been reserved on other nodes. > > Just curious, is it a real-life problem you've seen? If so, I wonder how > you're using the hugetlb_cma option, and what's the outcome?
Yes. It is kind of stupid but I once got a board on which node0 has no DDR though node1 and node3 have memory.
I actually prefer we get cma size of per node by: cma size of one node = hugetlb_cma/ (nodes with memory) rather than: cma size of one node = hugetlb_cma/ (all online nodes)
but unfortunately, or the N_MEMORY infrastructures are not ready yet. I mean:
for_each_node_state(nid, N_MEMORY) { int res;
size = min(per_node, hugetlb_cma_size - reserved); size = round_up(size, PAGE_SIZE << order);
res = cma_declare_contiguous_nid(0, size, 0, PAGE_SIZE << order, 0, false, "hugetlb", &hugetlb_cma[nid], nid); ... }
> > > > > Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages > using cma") > > Cc: Roman Gushchin <guro@fb.com> > > Cc: Mike Kravetz <mike.kravetz@oracle.com> > > Cc: Jonathan Cameron <jonathan.cameron@huawei.com> > > Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> > > --- > > mm/hugetlb.c | 18 +++++++++++++++--- > > 1 file changed, 15 insertions(+), 3 deletions(-) > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index 57ece74e3aae..603aa854aa89 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -2571,9 +2571,21 @@ static void __init > hugetlb_hstate_alloc_pages(struct hstate *h) > > > > for (i = 0; i < h->max_huge_pages; ++i) { > > if (hstate_is_gigantic(h)) { > > - if (IS_ENABLED(CONFIG_CMA) && hugetlb_cma[0]) { > > - pr_warn_once("HugeTLB: hugetlb_cma is enabled, skip > boot time allocation\n"); > > - break; > > + if (IS_ENABLED(CONFIG_CMA)) { > > + int nid; > > + bool cma_reserved = false; > > + > > + for_each_node_state(nid, N_ONLINE) { > > + if (hugetlb_cma[nid]) { > > + pr_warn_once("HugeTLB: hugetlb_cma is > reserved," > > + "skip boot time allocation\n"); > > + cma_reserved = true; > > + break; > > + } > > + } > > + > > + if (cma_reserved) > > + break; > > It's a valid problem, and I like to see it fixed. But I wonder if it would be better > to introduce a new helper bool hugetlb_cma_enabled()? And move both > IS_ENABLED(CONFIG_CMA) > and hugetlb_cma[nid] checks there?
Yep. that would be more readable.
> > Thank you!
Thanks Barry
| |