linux-kernel - Re: [PATCH v4] page_ext: introduce boot parameter 'early_page

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Date:   Thu, 25 Aug 2022 21:23:38 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     lizhe.67@...edance.com
Cc:     mhocko@...e.com, vbabka@...e.cz, mhiramat@...nel.org,
        keescook@...omium.org, Jason@...c4.com, mark-pk.tsai@...iatek.com,
        rostedt@...dmis.org, corbet@....net, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        lizefan.x@...edance.com
Subject: Re: [PATCH v4] page_ext: introduce boot parameter 'early_page_ext'

On Thu, 25 Aug 2022 18:27:14 +0800 lizhe.67@...edance.com wrote:

> From: Li Zhe <lizhe.67@...edance.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;
_