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 4CED940244A for ; Mon, 11 May 2026 15:41:08 +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=1778514068; cv=none; b=W35blWz2qjAzfzoWuNGaHcjrigBv4+L5/fiX21fsqSNaUAT/w4f0UqiEXJHkcmnRI0TbtrcaSZYNOuBmbuxV8kreGlVNCE0tjGjzcuecuYttZSGzOvfO9xeiZ9UfeAuKezJEqUJQgt7pjFQxBXAtohi41j8mFw7ZdCQHlpSVmeU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778514068; c=relaxed/simple; bh=3dAUWKuR756MvleFWo7H3QaP1i9/q+6aDhzkRJEueyI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=sbkwhOXTh129CdrdxZ+0DdkaZE64Uudb8Vtyfw3HcL+THHi3S50jKct6rn6nIDle7x+JZt0E5yIhc6qw7pCP6duKsjyfyLkbY9BlBVt4vW1yOOHep2IXOanoFzNlaL1UAsS6SeSKcc+RQiBtxZIy4edw4DGtXW3X7rGI19tNguQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gIGAlmpH; 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="gIGAlmpH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D113C2BCFF; Mon, 11 May 2026 15:41:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778514067; bh=3dAUWKuR756MvleFWo7H3QaP1i9/q+6aDhzkRJEueyI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=gIGAlmpHQ9fwoE8u5/k2Wn6ewPPNyo9bpLGiPfe4Yx+72vLm6jy3DAwys7XWmOEOg 15M9n+MZKpYqs/Y+6o5BAWs1sKgu0bW0Eu5IdGEFNDurK+xU0KP1qVFJyvMBvK68/M jPrkwgtA88YyuCqdOAWWXzZ+yY1fRhniMbb2XgIEy7Qv27ngxo20VY+7bTKEpihvTR Dw2QIZF7BoQh1/2IhaH7Fsk8P2IBw13ZTGVcVnqM5RGQgX0gwp1oNdiO5kvNaWBST5 nY7bgQHPwxk92uwt0LBqbwUGnly3gCXxzd+2svXI4vb4FHgkqAfJBAYyZZwUXNX+QD vIabhJVMgsswA== Message-ID: Date: Mon, 11 May 2026 17:40:58 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/7] mm/migrate: add batch-copy path in migrate_pages_batch To: Shivank Garg , akpm@linux-foundation.org Cc: kinseyho@google.com, weixugc@google.com, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, willy@infradead.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, dave@stgolabs.net, Jonathan.Cameron@huawei.com, rkodsara@amd.com, vkoul@kernel.org, bharata@amd.com, sj@kernel.org, rientjes@google.com, xuezhengchu@huawei.com, yiannis@zptcorp.com, dave.hansen@intel.com, hannes@cmpxchg.org, jhubbard@nvidia.com, peterx@redhat.com, riel@surriel.com, shakeel.butt@linux.dev, stalexan@redhat.com, tj@kernel.org, nifan.cxl@gmail.com, jic23@kernel.org, aneesh.kumar@kernel.org, nathan.lynch@amd.com, Frank.li@nxp.com, djbw@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260428155043.39251-2-shivankg@amd.com> <20260428155043.39251-10-shivankg@amd.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/28/26 17:50, Shivank Garg wrote: > Add folios_mc_copy() which walks list of src and dst folios in lockstep, > and copies folio content via folio_mc_copy(). folios_cnt parameter is > unused here, but is part of the offload_copy callback signature used by > later patches in the series. > > Split unmapped folios into batch-eligible (unmap_batch/dst_batch) and > standard (unmap_single/dst_single) lists, gated by the > migrate_offload_enabled which is off by default. So, when no offload > driver is active, the branch is never taken and everything goes > through the standard path. > > After TLB flush, batch copy the eligible folios via folios_mc_copy() > and pass already_copied=true into migrate_folios_move() so > __migrate_folio() skips the per-folio copy. > > On batch copy failure, already_copied flag stays false and each folio > fall back to individual copy. > > Signed-off-by: Shivank Garg > --- > include/linux/mm.h | 2 ++ > mm/migrate.c | 61 +++++++++++++++++++++++++++++++++++----------- > mm/util.c | 30 +++++++++++++++++++++++ > 3 files changed, 79 insertions(+), 14 deletions(-) [...] > > +DEFINE_STATIC_KEY_FALSE(migrate_offload_enabled); > + > static const struct movable_operations *offline_movable_ops; > static const struct movable_operations *zsmalloc_movable_ops; > > @@ -1724,6 +1727,12 @@ static int migrate_hugetlbs(struct list_head *from, new_folio_t get_new_folio, > return nr_failed; > } > > +/* movable_ops folios have their own migrate path */ > +static bool folio_supports_batch_copy(struct folio *folio) > +{ > + return likely(!page_has_movable_ops(&folio->page)); > +} As these things are not actually folios (and callers will have to be taught to distinguish them way, way earlier), I guess you should make this /* movable_ops pages have a separate migration path */ static bool page_supports_batch_copy(struct page *page) ... > + > static void migrate_folios_move(struct list_head *src_folios, > struct list_head *dst_folios, > free_folio_t put_new_folio, unsigned long private, > @@ -1752,7 +1761,7 @@ static void migrate_folios_move(struct list_head *src_folios, > /* > * The rules are: > * 0: folio will be freed > - * -EAGAIN: stay on the unmap_folios list > + * -EAGAIN: stay on the src_folios list > * Other errno: put on ret_folios list > */ > switch (rc) { [...] > --- a/mm/util.c > +++ b/mm/util.c > @@ -778,6 +778,36 @@ int folio_mc_copy(struct folio *dst, struct folio *src) > } > EXPORT_SYMBOL(folio_mc_copy); > > +/** > + * folios_mc_copy - Copy the contents of list of folios. > + * @dst_list: destination folio list. > + * @src_list: source folio list. > + * @folios_cnt: unused here, present for callback signature compatibility. > + * > + * Walks list of src and dst folios in lockstep and copies folio > + * content via folio_mc_copy(). The caller must ensure both lists have > + * the same number of entries. This may sleep. This *function* > + * > + * Return: 0 on success, negative errno on failure. > + */ > +int folios_mc_copy(struct list_head *dst_list, struct list_head *src_list, > + unsigned int __always_unused folios_cnt) > +{ > + struct folio *src, *dst; > + int ret; > + > + dst = list_first_entry(dst_list, struct folio, lru); > + list_for_each_entry(src, src_list, lru) { > + ret = folio_mc_copy(dst, src); > + if (ret) > + return ret; > + dst = list_next_entry(dst, lru); > + } Wouldn't it be cleaner to remember "already copied" immediately after we ... performed the copy? (succeeded with folio_mc_copy) -- Cheers, David