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Thu, 27 Jun 2024 06:00:34 GMT Received: from smtpav06.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7CCCE58054; Thu, 27 Jun 2024 06:00:29 +0000 (GMT) Received: from smtpav06.wdc07v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E53AF58064; Thu, 27 Jun 2024 06:00:27 +0000 (GMT) Received: from [9.109.245.191] (unknown [9.109.245.191]) by smtpav06.wdc07v.mail.ibm.com (Postfix) with ESMTP; Thu, 27 Jun 2024 06:00:27 +0000 (GMT) Message-ID: <4748f87e-0762-40fc-ab9e-577c9739066f@linux.ibm.com> Date: Thu, 27 Jun 2024 11:30:26 +0530 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 v1 2/2] mm/migrate: move NUMA hinting fault folio isolation + checks under PTL To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton References: <20240620212935.656243-1-david@redhat.com> <20240620212935.656243-3-david@redhat.com> <8f85c31a-e603-4578-bf49-136dae0d4b69@redhat.com> Content-Language: en-US From: Donet Tom In-Reply-To: <8f85c31a-e603-4578-bf49-136dae0d4b69@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 9aSEh46fcGJ41bHlYQSuh0XRIudn5-XY X-Proofpoint-GUID: fD3HInaw9n4W3uDLS0ODJ8G2glp2YjZz X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-06-27_02,2024-06-25_01,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 priorityscore=1501 mlxscore=0 phishscore=0 adultscore=0 mlxlogscore=999 impostorscore=0 suspectscore=0 clxscore=1015 spamscore=0 bulkscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2406270043 On 6/26/24 21:52, David Hildenbrand wrote: > On 20.06.24 23:29, David Hildenbrand wrote: >> Currently we always take a folio reference even if migration will not >> even be tried or isolation failed, requiring us to grab+drop an >> additional >> reference. >> >> Further, we end up calling folio_likely_mapped_shared() while the folio >> might have already been unmapped, because after we dropped the PTL, that >> can easily happen. We want to stop touching mapcounts and friends from >> such context, and only call folio_likely_mapped_shared() while the folio >> is still mapped: mapcount information is pretty much stale and >> unreliable >> otherwise. >> >> So let's move checks into numamigrate_isolate_folio(), rename that >> function to migrate_misplaced_folio_prepare(), and call that function >> from callsites where we call migrate_misplaced_folio(), but still with >> the PTL held. >> >> We can now stop taking temporary folio references, and really only take >> a reference if folio isolation succeeded. Doing the >> folio_likely_mapped_shared() + golio isolation under PT lock is now >> similar >> to how we handle MADV_PAGEOUT. >> >> While at it, combine the folio_is_file_lru() checks. >> >> Signed-off-by: David Hildenbrand >> --- > > Donet just reported an issue. I suspect this fixes it -- in any case, > this is > the right thing to do. > > From 0833b9896e98c8d88c521609c811a220d14a2e7e Mon Sep 17 00:00:00 2001 > From: David Hildenbrand > Date: Wed, 26 Jun 2024 18:14:44 +0200 > Subject: [PATCH] Fixup: mm/migrate: move NUMA hinting fault folio > isolation + >  checks under PTL > > Donet reports an issue during NUMA migration we haven't seen previously: > >     [   71.422804] list_del corruption, c00c00000061b3c8->next is >     LIST_POISON1 (5deadbeef0000100) >     [   71.422839] ------------[ cut here ]------------ >     [   71.422843] kernel BUG at lib/list_debug.c:56! >     [   71.422850] Oops: Exception in kernel mode, sig: 5 [#1] > > We forgot to convert one "return 0;" to return an error instead from > migrate_misplaced_folio_prepare() in case the target node is nearly > full. > > Signed-off-by: David Hildenbrand > --- >  mm/migrate.c | 2 +- >  1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 8beedbb42a93..9ed43c1eea5e 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2564,7 +2564,7 @@ int migrate_misplaced_folio_prepare(struct folio > *folio, >          int z; > >          if (!(sysctl_numa_balancing_mode & > NUMA_BALANCING_MEMORY_TIERING)) > -            return 0; > +            return -EAGAIN; >          for (z = pgdat->nr_zones - 1; z >= 0; z--) { >              if (managed_zone(pgdat->node_zones + z)) >                  break; Hi David I tested with this patch . The issue is resolved. I am not seeing the kernel panic. I also tested the page migration. It working fine. numa_pte_updates 1262330 numa_huge_pte_updates 0 numa_hint_faults 925797 numa_hint_faults_local 3780 numa_pages_migrated 327930 pgmigrate_success 822530 Thanks Donet > > base-commit: 4b17ce353e02b47b00e2fe87b862f09e8b9a47e6