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 6D90D288C39; Sat, 14 Mar 2026 22:40:44 +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=1773528044; cv=none; b=ch7REdsorb1KU5/P5qdZ+kIqistoYSaW1MKi4+KwL5nJtiGWL+GUhMntrlfZoBaFFVAIOMwzIsWllUMomDLZOdf01wbJ47x59BsxC/KuGJKMcFCFj9HuyrndEga6v32TUmt7pkp02B6YxPvNDjz1K8NkVLVX9OD+jOCXTODhcYY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773528044; c=relaxed/simple; bh=sV9PTCvMW2uwYIYWoDT7NCvHOX9y6njZbgMbRie3eZw=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=fvtRv3IAq9FrNs1pgvajPrZSIvARkYaIwQHE4GgFhF8Bvmg3YV8GoruMvGczG+o00RWKpHahwavqCxVzyjbEsrH6JMam3eV5TQHjNAv9xRH/2HHwEsQQvTGWRj0lETABUp6NHvaTT3ANqwL2UnFepUGFJ1tXODqpZDqz2c5Szbo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=iynWM0D4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="iynWM0D4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A489C116C6; Sat, 14 Mar 2026 22:40:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1773528044; bh=sV9PTCvMW2uwYIYWoDT7NCvHOX9y6njZbgMbRie3eZw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=iynWM0D4SUypA8wlnsvN9Nb8wXTGYvUrZyHq3YXnX4a0GasUjitdrA6P4X/aXdVlJ Uty182SdFlDkGEHq8oVt4FYAu0vfPMp+tZKOE9iUJCLbHXMD0JofkLOyoRWljN8aUH HmTETDXB607mjyh8boIhMKHTnk5lUM6C/K5yNkVA= Date: Sat, 14 Mar 2026 15:40:42 -0700 From: Andrew Morton To: Usama Arif Cc: SeongJae Park , npache@redhat.com, david@kernel.org, ziy@nvidia.com, willy@infradead.org, linux-mm@kvack.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, hannes@cmpxchg.org, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-kernel@vger.kernel.org, kernel-team@meta.com, richard.weiyang@gmail.com, stable@vger.kernel.org Subject: Re: [PATCH v3] mm: migrate: requeue destination folio on deferred split queue Message-Id: <20260314154042.327ba957b1a8c10f64ae0169@linux-foundation.org> In-Reply-To: References: <20260312104723.1351321-1-usama.arif@linux.dev> <20260313001630.80081-1-sj@kernel.org> <20260312175241.01b876f3b325264f43312d79@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 13 Mar 2026 13:40:29 +0300 Usama Arif wrote: > > > On 13/03/2026 03:52, Andrew Morton wrote: > > On Thu, 12 Mar 2026 17:16:30 -0700 SeongJae Park wrote: > > > >>> By the time migrate_folio_move() runs, partially mapped folios without a > >>> pin have already been split by migrate_pages_batch(). So only two cases > >>> remain on the deferred list at this point: > >>> 1. Partially mapped folios with a pin (split failed). > >>> 2. Fully mapped but potentially underused folios. > >>> The recorded partially_mapped state is forwarded to deferred_split_folio() > >>> so that the destination folio is correctly re-queued in both cases. > >>> > >>> Reported-by: Johannes Weiner > >>> Fixes: dafff3f4c850 ("mm: split underused THPs") > >> > >> Seems the commit is merged in 6.12. And I assume the user impact on > >> THP-shrinker enabled systems is visible. If so, should we Cc stable@ ? > > > > I think the user impact should be visible to backport, but the > > changelog is elusive on details? > > > > > The original patches added THPs to deferred_list at fault/collapse, they > got removed but not added back to the list after migration. > This patch adds them to the deferred_list on migration. The user would > not expect the THPs to get removed from deferred_list on migration, so > this fixes user expectations. Maybe users just won't notice? If we can't identify any benefit to userspace then I don't think this patch meets the criteria for backporting. > I have CC-ed stable@vger.kernel.org to this email. Should I resend the patch > with CC stable in commit message? That's OK, I update changelogs. A lot.