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Tue, 30 Mar 2021 14:42:08 +0000 (GMT) Received: from thinkpad (unknown [9.171.41.230]) by d06av23.portsmouth.uk.ibm.com (Postfix) with SMTP; Tue, 30 Mar 2021 14:42:08 +0000 (GMT) Date: Tue, 30 Mar 2021 16:42:07 +0200 From: Gerald Schaefer To: Yang Shi Cc: mgorman@suse.de, kirill.shutemov@linux.intel.com, ziy@nvidia.com, mhocko@suse.com, ying.huang@intel.com, hughd@google.com, hca@linux.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Alexander Gordeev Subject: Re: [PATCH 5/6] mm: migrate: don't split THP for misplaced NUMA page Message-ID: <20210330164207.3a2826f7@thinkpad> In-Reply-To: <20210329183312.178266-6-shy828301@gmail.com> References: <20210329183312.178266-1-shy828301@gmail.com> <20210329183312.178266-6-shy828301@gmail.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: GTLsRE-t3jKQmmrgEXa1bXyawU1Xg_HM X-Proofpoint-ORIG-GUID: QA4EJPs-o2GZJ_Ndz7oaZ4WGu5lBPCKq X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-03-30_04:2021-03-30,2021-03-30 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 phishscore=0 impostorscore=0 bulkscore=0 suspectscore=0 clxscore=1015 priorityscore=1501 mlxscore=0 mlxlogscore=999 adultscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2103250000 definitions=main-2103300107 X-Rspamd-Queue-Id: D50EAA0009E3 X-Stat-Signature: x6pq8wxeua9n9drj8hjcf4zk33kdjc6r X-Rspamd-Server: rspam02 Received-SPF: none (linux.ibm.com>: No applicable sender policy available) receiver=imf24; identity=mailfrom; envelope-from=""; helo=mx0a-001b2d01.pphosted.com; client-ip=148.163.156.1 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617115333-548476 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: On Mon, 29 Mar 2021 11:33:11 -0700 Yang Shi wrote: > The old behavior didn't split THP if migration is failed due to lack of > memory on the target node. But the THP migration does split THP, so keep > the old behavior for misplaced NUMA page migration. > > Signed-off-by: Yang Shi > --- > mm/migrate.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 86325c750c14..1c0c873375ab 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1444,6 +1444,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > int swapwrite = current->flags & PF_SWAPWRITE; > int rc, nr_subpages; > LIST_HEAD(ret_pages); > + bool nosplit = (reason == MR_NUMA_MISPLACED); > > if (!swapwrite) > current->flags |= PF_SWAPWRITE; > @@ -1495,7 +1496,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, > */ > case -ENOSYS: > /* THP migration is unsupported */ > - if (is_thp) { > + if (is_thp && !nosplit) { This is the "THP migration is unsupported" case, but according to your description you rather want to change the -ENOMEM case? Could this be the correct place to trigger THP split for NUMA balancing, for architectures not supporting THP migration, like s390? Do I understand it correctly that this change (for -ENOSYS) would result in always failed THP migrations during NUMA balancing, if THP migration was not supported?