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Tue, 22 Apr 2025 17:08:13 +0800 (CST) Date: Tue, 22 Apr 2025 17:08:06 +0800 From: Ruihan Li To: Mike Rapoport Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ruihan Li Subject: Re: [PATCH v2] mm/mm_init: Don't iterate pages below ARCH_PFN_OFFSET Message-ID: References: <20250419122801.1752234-1-lrh2000@pku.edu.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CM-TRANSID:5oFpogBHEcZ3XAdoYrFxAA--.50827S2 X-CM-SenderInfo: yssqiiarrvmko6sn3hxhgxhubq/1tbiAgEIBWf35XUDOwAgsW X-CM-DELIVERINFO: =?B?OSVrjqaAH6dYjNjDbLdWX9VB7ttaQFyXTaecYZzOeDisy/krtsX5TsLkpeAzENeCPc 0+BDdXjm5Mlm64oODP/CxX7CdHrAr06XGcwRbF9fF2WKf3sOM4KfjVzXEXUZJNGnDxNS+C CLbkwtEUkO2DmRqJzedd8mz6gv+Cykv5cvqS1q3k21LQR7vDiuSLjtOS7+y72w== X-Coremail-Antispam: 1Uk129KBjDUn29KB7ZKAUJUUUUU529EdanIXcx71UUUUU7KY7 ZEXasCq-sGcSsGvfJ3UbIjqfuFe4nvWSU5nxnvy29KBjDU0xBIdaVrnUUvcSsGvfC2Kfnx nUUI43ZEXa7xR_UUUUUUUUU== X-Rspam-User: X-Rspamd-Queue-Id: 9D31240003 X-Rspamd-Server: rspam04 X-Stat-Signature: gqorggw3zg3yg1orf9kwyqrr5hj6x6h8 X-HE-Tag: 1745312903-895456 X-HE-Meta: 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 jCbVvOmX 1+H1wOSQxiK+gJ+vF9D/eSuKrfgcTFdV/0yHtXYd15Ce5EDwRBrC9aQbEJzowqW8MH0J5RvtcqcbqUWVWn4fSS0XMuQLUA3rmj68KF3kUn55XvxcZRrNsOJusrA2RIwVHMed6wGCbXsr4DHjIOVv0bCeMv7JLQ4MGW3IX/z7uVWx7+Qms6UfxzxnkMD48CplQeCec3yxc1CZDY8HuJBlb/eyWmOtrAfcJpIU50weEhRXSAQpb5H0cMLigeiKuQ7w9NlVSC+bV/c78hjqEqAaaBTPumXlJZ7gHKmwtKQ/tjrZx2vm0QYT+bZ7Jy4YP+M6ggVQhYP8P6Mkszr33kAVZEcQ96AvSN/U9kiJnB89MRBZcao3d4+MTnLHrucWGudTTm0rrC1n5qeP+BXFUBe+hzLaD0Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Mike, Thanks for your review! On Mon, Apr 21, 2025 at 07:41:43PM +0300, Mike Rapoport wrote: > On Sat, Apr 19, 2025 at 08:28:01PM +0800, Ruihan Li wrote: > > Currently, memmap_init initializes pfn_hole with 0 instead of > > ARCH_PFN_OFFSET. Then init_unavailable_range will start iterating each > > page from the page at address zero to the first available page, but it > > won't do anything for pages below ARCH_PFN_OFFSET because pfn_valid > > won't pass. > > > > If ARCH_PFN_OFFSET is very large (e.g., something like 2^64-2GiB if the > > kernel is used as a library and loaded at a very high address), the > > pointless iteration for pages below ARCH_PFN_OFFSET will take a very > > long time, and the kernel will look stuck at boot time. > > > > This commit sets the initial value of pfn_hole to ARCH_PFN_OFFSET, which > > avoids the problematic and useless iteration mentioned above. > > > > This problem has existed since commit 907ec5fca3dc ("mm: zero remaining > > unavailable struct pages"). > > > > Signed-off-by: Ruihan Li > > --- > > Link to v1: > > - https://lore.kernel.org/linux-mm/20250418162727.1535335-1-lrh2000@pku.edu.cn/ > > Changes since v1: > > - Removed the unnecessary Fixes tag. > > - Fixed the build issue for CONFIG_SPARSEMEM. > > > > mm/mm_init.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/mm/mm_init.c b/mm/mm_init.c > > index 84f14fa12..a697a83ff 100644 > > --- a/mm/mm_init.c > > +++ b/mm/mm_init.c > > @@ -969,6 +969,15 @@ static void __init memmap_init(void) > > unsigned long hole_pfn = 0; > > int i, j, zone_id = 0, nid; > > > > +#ifdef CONFIG_FLATMEM > > + /* > > + * Pages below ARCH_PFN_OFFSET are invalid as far as pfn_valid is > > + * concerned, so don't waste time iterating on them when looking > > + * for holes. > > + */ > > + hole_pfn = ARCH_PFN_OFFSET; > > +#endif > > + > > I'd prefer a solution for both FLATMEM and SPARSMEM. > > David Woodhouse proposed a for_each_valid_pfn() a while ago: > > https://lore.kernel.org/all/20250404155959.3442111-1-dwmw2@infradead.org > > It can be used in init_unavailable_range() and will essentially skip the > unpopulated memory map. for_each_valid_pfn sounds much better. Thanks for your input. However, the problem is that David's patch is not showing up in the mainline, so what can I do to move forward with my patch? Perhaps you mean that I should wait until David's patch is merged and send another patch to fix the problem? > > > for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) { > > struct pglist_data *node = NODE_DATA(nid); > > > > -- > > 2.49.0 > > > > -- > Sincerely yours, > Mike. Thanks, Ruihan Li