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Tue, 01 Jun 2021 06:51:59 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 1516pvwh18284922 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 1 Jun 2021 06:51:57 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 10D7E11C052; Tue, 1 Jun 2021 06:51:57 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A494F11C04A; Tue, 1 Jun 2021 06:51:54 +0000 (GMT) Received: from bharata.ibmuc.com (unknown [9.77.195.136]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 1 Jun 2021 06:51:54 +0000 (GMT) From: Bharata B Rao To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, aneesh.kumar@linux.ibm.com, dennis@kernel.org, tj@kernel.org, cl@linux.com, akpm@linux-foundation.org, amakhalov@vmware.com, guro@fb.com, vbabka@suse.cz, srikar@linux.vnet.ibm.com, psampat@linux.ibm.com, ego@linux.vnet.ibm.com, Bharata B Rao Subject: [RFC PATCH v0 0/3] CPU hotplug awareness in percpu allocator Date: Tue, 1 Jun 2021 12:21:44 +0530 Message-Id: <20210601065147.53735-1-bharata@linux.ibm.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 1nuTsGCkU2yfKAHJ1afVLZpl4yivEbPH X-Proofpoint-GUID: 1nuTsGCkU2yfKAHJ1afVLZpl4yivEbPH X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-01_03:2021-05-31,2021-06-01 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 lowpriorityscore=0 phishscore=0 clxscore=1011 mlxlogscore=999 impostorscore=0 spamscore=0 malwarescore=0 mlxscore=0 bulkscore=0 suspectscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106010045 Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=ibm.com header.s=pp1 header.b=DW+u5irG; spf=pass (imf08.hostedemail.com: domain of bharata@linux.ibm.com designates 148.163.158.5 as permitted sender) smtp.mailfrom=bharata@linux.ibm.com; dmarc=pass (policy=none) header.from=ibm.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 4917E8019364 X-Stat-Signature: e56ssks8xzd4a445ttpqkzdbfd8xhewy X-HE-Tag: 1622530317-397916 Content-Transfer-Encoding: quoted-printable 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: Hi, This is an attempt to make the percpu allocator CPU hotplug aware. Currently the percpu allocator allocates memory for all the possible CPUs. This can lead to wastage of memory when possible number of CPUs is significantly higher than the number of online CPUs. This can be avoided if the percpu allocator were to allocate only for the online CPUs and extend the allocation for other CPUs as and when they become online.=20 This early RFC work shows some good memory savings for a powerpc KVM guest that is booted with 16 online and 1024 possible CPUs. Here is the comparision of Percpu memory consumption from /proc/meminfo before and after creating 1000 memcgs. W/o patch W/ patch Before 1441792 kB 22528 kB After 1000 memcgs 4390912 kB 68608 kB Note that the Percpu reporting in meminfo has been changed in the patchset to reflect the allocation for online CPUs only. More details about the approach are present in the patch descriptions. Bharata B Rao (3): percpu: CPU hotplug support for alloc_percpu() percpu: Limit percpu allocator to online cpus percpu: Avoid using percpu ptrs of non-existing cpus fs/namespace.c | 4 +- include/linux/cpuhotplug.h | 2 + include/linux/percpu.h | 15 +++ kernel/cgroup/rstat.c | 20 +++- kernel/sched/cpuacct.c | 10 +- kernel/sched/psi.c | 14 ++- lib/percpu-refcount.c | 4 +- lib/percpu_counter.c | 2 +- mm/percpu-internal.h | 9 ++ mm/percpu-vm.c | 211 +++++++++++++++++++++++++++++++++- mm/percpu.c | 229 +++++++++++++++++++++++++++++++++++-- net/ipv4/fib_semantics.c | 2 +- net/ipv6/route.c | 6 +- 13 files changed, 490 insertions(+), 38 deletions(-) --=20 2.31.1