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Date:   Thu, 25 Aug 2022 21:23:38 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     lizhe.67@bytedance.com
Cc:     mhocko@suse.com, vbabka@suse.cz, mhiramat@kernel.org,
        keescook@chromium.org, Jason@zx2c4.com, mark-pk.tsai@mediatek.com,
        rostedt@goodmis.org, corbet@lwn.net, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        lizefan.x@bytedance.com
Subject: Re: [PATCH v4] page_ext: introduce boot parameter 'early_page_ext'
Message-Id: <20220825212338.e541d29ca3c4d602221f4925@linux-foundation.org>
In-Reply-To: <20220825102714.669-1-lizhe.67@bytedance.com>
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On Thu, 25 Aug 2022 18:27:14 +0800 lizhe.67@bytedance.com wrote:

> From: Li Zhe <lizhe.67@bytedance.com>
> 
> In 'commit 2f1ee0913ce5 ("Revert "mm: use early_pfn_to_nid in page_ext_init"")',
> we call page_ext_init() after page_alloc_init_late() to avoid some panic
> problem. It seems that we cannot track early page allocations in current
> kernel even if page structure has been initialized early.
> 
> This patch introduce a new boot parameter 'early_page_ext' to resolve this
> problem. If we pass it to kernel, function page_ext_init() will be moved
> up and feature 'deferred initialization of struct pages' will be disabled
> to initialize the page allocator early and prevent from the panic problem
> above. It can help us to catch early page allocations. This is useful
> especially when we find that the free memory value is not the same right
> after different kernel booting.
> 

WARNING: modpost: vmlinux.o: section mismatch in reference: early_page_ext_enabled (section: .text.unlikely) -> early_page_ext (section: .meminit.data)
WARNING: modpost: vmlinux.o: section mismatch in reference: early_page_ext_enabled (section: .text.unlikely) -> early_page_ext (section: .meminit.data)

I did this, but it was lazy - perhaps there's a better-optimized
combination of section tags.  Please check?

--- a/mm/page_ext.c~page_ext-introduce-boot-parameter-early_page_ext-fix
+++ a/mm/page_ext.c
@@ -91,7 +91,7 @@ unsigned long page_ext_size = sizeof(str
 static unsigned long total_usage;
 static struct page_ext *lookup_page_ext(const struct page *page);
 
-bool early_page_ext __meminitdata;
+bool early_page_ext;
 static int __init setup_early_page_ext(char *str)
 {
 	early_page_ext = true;
_