From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B1BA51A682C for ; Wed, 29 Apr 2026 00:57:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777424268; cv=none; b=CaTcPGcJHCwb4cV7iTIZt/Tj98U2cADCPXkUEY/ejr4zvNG+HWNp2w7ysUbtOQZWrulUPxAn1IAlz/sGjKyQdjfm3NWZzhUftFW2Nb6QvA0h76zCJLWaRieC7j1imkzLgRLYq9jfCQZXODA7srBVnROTNG0ETbMSrEQb4myXcqc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777424268; c=relaxed/simple; bh=dR3dNMwJfMpAWCWRKlY+edR9MACregw8U7mpdn1y6B0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=E35rrKU0UMnfqj/rm8X8kmKElGlVjp+7YVt0vtJa3+8i/sTYF4iE95ra9M/lHswaoTV1sP8M4buVDteSWZx/rC/irDpITkSoItQPozgpdQyVDcjPAMtXlcQXL2dy9IgKIuj5G4BF4P+e13UBtShBwX2rabzfJIOxJ78zMZlUgbE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=D64EpzZi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="D64EpzZi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5695C2BCAF; Wed, 29 Apr 2026 00:57:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777424268; bh=dR3dNMwJfMpAWCWRKlY+edR9MACregw8U7mpdn1y6B0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D64EpzZi5Bhi6P6rHpHmpixMeLLgFKmHe1aQgRErW5NJz9wyrZEAfeR+I9jWSVpMU M3cQnc77z38xrPy0p9g8VeCwGbnjQ57phC62IonusCds9oD6Pb1dOBCLcoi6hESGpt cmfWHxcc31fn27x57R5WxtZz9a7lURqj0gMIwunFl3rXD1f8bs0oUqSs6wTVjl46UL NHJirKBdPvHfykiStSxTusv0GrwFXglOi+OPoLama1+GDlIPV18TamYpMiXwm5KaJh 7ncpyMxD9EvhkQETuyUMo4/TmLL7kLoc7tAcj+FKMeB2NwilO6dN+JFPoNYAxJfRPL 3RWBnYX3FrD0Q== From: SeongJae Park To: Zhen Ni Cc: SeongJae Park , akpm@linux-foundation.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/4] mm/page_owner: add print_mode filter Date: Tue, 28 Apr 2026 17:57:38 -0700 Message-ID: <20260429005739.88517-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260428071112.1420380-3-zhen.ni@easystack.cn> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, 28 Apr 2026 15:11:10 +0800 Zhen Ni wrote: > Add print_mode functionality to reduce page_owner output size by > printing only the stack handle instead of the full stack trace. > > Example output with print_mode enabled: > Page allocated via order 0, mask 0x42800(GFP_NOWAIT|__GFP_COMP), > pid 1, tgid 1 (systemd), ts 349667370 ns > PFN 0xa00a2 type Unmovable Block 1280 type Unmovable > Flags 0x33fffe0000004124(referenced|lru|active|private|node=3|zone=0| > lastcpupid=0x1ffff) > handle: 17432583 > Charged to memcg / Looks nice to me. I have just trivial cosmetic comments below. > > Print mode significantly reduces output size while preserving all > other page allocation information. The correspondence between handles > and stack traces can be obtained through the show_stacks_handles interface. I understand the mode was introduced for the stack handle mode, but it exists for both full stack and stack handle mode? The wording makes me assume the mode is only enabled vs disabled (boolean). It is true that there are only two modes, but I feel like this commit message might better written. > > Link: https://lore.kernel.org/linux-mm/20260417154638.22370-3-zhen.ni@easystack.cn/ Seems this is a link to v1 of this patch. I think adding the context or moving this to the changelog [1] with the brief context explanation would be nice. > Suggested-by: Zi Yan > Signed-off-by: Zhen Ni > --- > > Changes in v2: > - Renamed from 'compact mode' to 'print_mode' for better clarity > - Use enum values (0=full_stack, 1=stack_handle) instead of boolean > - Update debugfs filename from 'compact' to 'print_mode' > > Changes in v3: > - No code changes > --- > mm/page_owner.c | 28 +++++++++++++++++++++++++++- > 1 file changed, 27 insertions(+), 1 deletion(-) > > diff --git a/mm/page_owner.c b/mm/page_owner.c > index 5884d883837e..6d87b6948cfa 100644 > --- a/mm/page_owner.c > +++ b/mm/page_owner.c > @@ -590,7 +590,13 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn, > migratetype_names[pageblock_mt], > &page->flags); > > - ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0); > + /* Print mode: full stack or stack handle */ I think this comment should be useful if it was compact_mode. But because now it is called print_mode and values have good names that self explaining what the mode is, I'm not sure if this comment is really needed. > + if (READ_ONCE(owner_filter.print_mode) == PAGE_OWNER_PRINT_STACK_HANDLE) { > + ret += scnprintf(kbuf + ret, count - ret, > + "handle: %d\n", handle); > + } else { > + ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0); > + } Braces are not needed [2] here? > if (ret >= count) > goto err; > > @@ -985,6 +991,24 @@ static int page_owner_threshold_set(void *data, u64 val) > DEFINE_SIMPLE_ATTRIBUTE(page_owner_threshold_fops, &page_owner_threshold_get, > &page_owner_threshold_set, "%llu"); > > +static int page_owner_print_mode_get(void *data, u64 *val) > +{ > + *val = READ_ONCE(owner_filter.print_mode); > + return 0; > +} > + > +static int page_owner_print_mode_set(void *data, u64 val) > +{ > + if (val > PAGE_OWNER_PRINT_STACK_HANDLE) > + return -EINVAL; > + WRITE_ONCE(owner_filter.print_mode, val); > + return 0; > +} > + > +DEFINE_SIMPLE_ATTRIBUTE(page_owner_print_mode_fops, > + &page_owner_print_mode_get, > + &page_owner_print_mode_set, "%lld"); > + > > static int __init pageowner_init(void) > { > @@ -998,6 +1022,8 @@ static int __init pageowner_init(void) > debugfs_create_file("page_owner", 0400, NULL, NULL, &page_owner_fops); > > filter_dir = debugfs_create_dir("page_owner_filter", NULL); > + debugfs_create_file("print_mode", 0600, filter_dir, NULL, > + &page_owner_print_mode_fops); > > dir = debugfs_create_dir("page_owner_stacks", NULL); > debugfs_create_file("show_stacks", 0400, dir, > -- > 2.20.1 [1] https://docs.kernel.org/process/submitting-patches.html#commentary [2] https://docs.kernel.org/process/coding-style.html#placing-braces-and-spaces Thanks, SJ