Re: [PATCH 1/2] mm: Guard a use of node_reclaim_distance with CONFIFG_NUMA
From: Andrew Morton
Date: Fri Feb 26 2021 - 15:38:21 EST
On 2021年2月26日 12:17:20 -0800 Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
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From: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
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This is only useful under CONFIG_NUMA. IIUC skipping the check is the
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right thing to do here, as without CONFIG_NUMA there will never be any
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large node distances on non-NUMA systems.
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I expected this to manifest as a link failure under (!CONFIG_NUMA &&
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CONFIG_TRANSPARENT_HUGE_PAGES), but I'm not actually seeing that. I
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think the reference is just getting pruned before it's checked, but I
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didn't get that from reading the code so I'm worried I'm missing
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something.
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Either way, this is necessary to guard the definition of
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node_reclaim_distance with CONFIG_NUMA.
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Signed-off-by: Palmer Dabbelt <palmerdabbelt@xxxxxxxxxx>
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---
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mm/khugepaged.c | 2 ++
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1 file changed, 2 insertions(+)
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diff --git a/mm/khugepaged.c b/mm/khugepaged.c
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index a7d6cb912b05..b1bf191c3a54 100644
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--- a/mm/khugepaged.c
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+++ b/mm/khugepaged.c
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@@ -819,8 +819,10 @@ static bool khugepaged_scan_abort(int nid)
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for (i = 0; i < MAX_NUMNODES; i++) {
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if (!khugepaged_node_load[i])
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continue;
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+#ifdef CONFIG_NUMA
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if (node_distance(nid, i) > node_reclaim_distance)
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return true;
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+#endif
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}
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return false;
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}
This makes the entire loop a no-op. Perhaps Kirill can help take a
look at removing unnecessary code in khugepaged.c when CONFIG_NUMA=n?