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Wed, 28 Jun 2023 10:27:49 GMT Received: from smtpav03.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1BB2358056; Wed, 28 Jun 2023 10:27:49 +0000 (GMT) Received: from smtpav03.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2FE885803F; Wed, 28 Jun 2023 10:27:44 +0000 (GMT) Received: from patel.in.ibm.com (unknown [9.109.195.224]) by smtpav03.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 28 Jun 2023 10:27:43 +0000 (GMT) Message-ID: <3cc8a00a7ca17417711f921717c3ab34fae5d7ed.camel@linux.ibm.com> Subject: Re: [RFC PATCH ] mm/slub: Reducing slub memory wastage From: Jay Patel Reply-To: jaypatel@linux.ibm.com To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: linux-mm@kvack.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, aneesh.kumar@linux.ibm.com, tsahu@linux.ibm.com, piyushs@linux.ibm.com, roman.gushchin@linux.dev Date: Wed, 28 Jun 2023 15:57:42 +0530 In-Reply-To: References: <20230612085535.275206-1-jaypatel@linux.ibm.com> <51045addfd3ec7804bcc36daed5827bf51095b68.camel@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5 (3.28.5-22.el8) X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: e0Sj1v49JQjXzloAKbnqnATO2_Qgfe3z X-Proofpoint-GUID: ktYdqX47KmT-6wync69TYG72C4WZ0p3F Content-Transfer-Encoding: 7bit X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.591,FMLib:17.11.176.26 definitions=2023-06-28_06,2023-06-27_01,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1011 suspectscore=0 impostorscore=0 mlxlogscore=980 lowpriorityscore=0 adultscore=0 mlxscore=0 phishscore=0 spamscore=0 malwarescore=0 priorityscore=1501 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2305260000 definitions=main-2306280088 X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: CECD8180008 X-Stat-Signature: xr7umgogj4bmaf1ehuhes4kkr5xyo1kn X-HE-Tag: 1687948075-190707 X-HE-Meta: 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 KnqztsLV wt/uFg1i0G42obsioqv5gkTcRgCtpj+MVMrc7ZD5hUOHypJoeNLdUITamjKsPmD/8XIqnQ7iYs5ApVl77v2J+jgp5EgPzlrGafw8zKImi9zt4+S5tcMrAW2sJ87qHehhRK9D0CH8/Frt0J+/uTLP3U9M8cwxqCVkixlFTzArHQ0h2b+OIXX11GjmnUZxX9i18Z72Ql8XUD6kW33oZxHtm7PxosX7MnNC82eV2M9q3yAx/zKjAnDZ6sBqqBoYxgugziUn1cwB9MaiU7rP/yO6MT3O3NyPGTDzK+ZPA/0YllHVVA5hCVzyRCFLSMmwXD9bLs2axzZVFatEU4WHdyZXEFxCxYmto5BgHZJPmwzRk+Gk8M5OgR1TQWCjxvCz1ac5cOMcGh/AoXYM3dDoP4zcAp+zwW4vYi/yt7das2vM42SGhK2zjqkLBxyLodDaLynxztObEShyR9T6pNbM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 2023-06-19 at 12:25 +0900, Hyeonggon Yoo wrote: > On Tue, Jun 13, 2023 at 06:25:48PM +0530, Jay Patel wrote: > > > <...snip...> > > > > I conducted tests on systems with 160 CPUs and 16 CPUs, > > > > using 4K > > > > and > > > > 64K page sizes. Through these tests, it was observed that the > > > > patch > > > > successfully reduces the wastage of slab memory without any > > > > noticeable > > > > performance degradation in the hackbench test report. However, > > > > it > > > > should > > > > be noted that the patch also increases the total number of > > > > objects, > > > > leading to an overall increase in total slab memory usage. > > > > > > <...snip...> > > > > > > Then my question is that, why is this a useful change if total > > > memory > > > usage is increased? > > > > > This patch aimed in reducing memory wastage can potentially lead to > > an > > increase in the slab order for a slab cache. Consequently, this > > increase in page order can result in a higher number of objects per > > slab, reducing wastage and leading to a more efficient utilization > > of > > memory. > > if you define utilization as percentage of memory that is > being used out of total memory, utilization becomes worse... (based > on data you provided) > > I think 'less memory wastage' is a useful feature only if the total > memory usage is reduced so that it could be used for other purposes. > > I mean, if it consumes more memory on a same workload (in most > cases), > who would like it? Hi Hyeonggon, Thank you for your response. I acknowledge your feedback, and I have made the necessary modifications to the patch. I am pleased to inform you that I have sent the updated version [1], which addresses the issues we discussed. [1] https://lore.kernel.org/linux-mm/20230628095740.589893-1-jaypatel@linux.ibm.com/T/#u Thanks, Jay Patel > > > This enhancement is advantageous since the presence of unused > > objects can be leveraged in the future, depending on varying > > workloads. > > At least we need to know when it is leveraged and what kinds of > workloads > would benefit... > > Thanks, >