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bh=sP+elCVD82x/GULcaOvWEpGNwwM1mOq6mIvqiIwxppg=; b=ULU0XeizzHQHzH73xjp7XXWMMbL0cnDXhmacXesiSXE0RcCxPTdzBEvIMHfdbW56d2FdJC SFbyGjFVgFqg5ocLFp7uI/sor9hsmpO5NvOtpMHEoTqMUQMHagVByIqYHHXdID+cc0EsGv VJOBcPT2U6DXWOXCgaEfq2deZ21SgUw= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=WqpHDmwv; spf=pass (imf27.hostedemail.com: domain of akpm@linux-foundation.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 36CDD44432; Mon, 30 Mar 2026 20:48:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0666DC2BCB2; Mon, 30 Mar 2026 20:48:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1774903694; bh=AaC4BteHAcUMtfgTBPqFhez5N/O8Wu9jNTP2fUEP0Yo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=WqpHDmwvIXKW+/jzj3WX55uyQ7jmHFcCXPRwU9/+TETEGtCBj+oqTTc1jLpzQy5pL NORSQfbfFyImibCOwO+wzQYp5NuHyuYsSHsYxnBVgDCgoYsxYTF/cKtexdbLU4hP2W 669EEaI5PuvaW+cpqXI1bTvyNxK2Rfxs3y7ao7OQ= Date: Mon, 30 Mar 2026 13:48:13 -0700 From: Andrew Morton To: Jiayuan Liang Cc: linux-mm@kvack.org Subject: Re: [PATCH v2] mm/page_owner: warn when stack trace depth hits PAGE_OWNER_STACK_DEPTH limit Message-Id: <20260330134813.084a2becac8ffc3cca99e1d5@linux-foundation.org> In-Reply-To: <20260328214408.2990597-1-ljykernel@163.com> References: <20260328214408.2990597-1-ljykernel@163.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 434C340005 X-Stat-Signature: mo1oeugn8nq871kir3uaqynwu6bsar9g X-HE-Tag: 1774903695-607117 X-HE-Meta: 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 8WD2TBJY T1fomN56x2eVh1pLJ+OriGGbAwSM1DDvXjad3HeoXmNr/dg6vGcFAOTCGBZra2c8qcfH24pdKOBKU3WSKowhgcYZdAijcqgwL814CCFruFvEHtN5P449KpzQkERn/9yznBO0oS9E2EyitbYO5AdBRpdVIHm49JVdnODn7GKC8KWnDltNtiAo7dwrJXr8YSVrQPgTYEp0CAVNHLxodE8iwlLHuQSm7lEheHIHzh5BUyHp9dnuAmBlUn9854TEFRH5huasBWG/F/8zrZAdSxy0vHgQbsH209+4I5SJDGa8pw19OyKVV6RCJY6vRNh6SmvuEKeoA Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 29 Mar 2026 05:44:08 +0800 Jiayuan Liang wrote: > page_owner silently truncates stack traces deeper than > PAGE_OWNER_STACK_DEPTH (16), which hides root caller information during > memory debugging. > > Add a ratelimited warning to notify developers when this truncation occurs. > > ... > > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -163,6 +163,9 @@ static noinline depot_stack_handle_t save_stack(gfp_t flags) > > set_current_in_page_owner(); > nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2); > + if (nr_entries >= PAGE_OWNER_STACK_DEPTH) > + pr_warn_ratelimited("page_owner: stack depth %u exceeds limit %u\n", > + nr_entries, PAGE_OWNER_STACK_DEPTH); > handle = stack_depot_save(entries, nr_entries, flags); > if (!handle) > handle = failure_handle; Is it ideal to emit this warning in real time? Would it be better to tell the user "this was truncated" when they actually _use_ the data? Presumably this would require alteration to page_owner_sort.c and page_owner.rst.