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Thu, 16 Jan 2025 11:16:52 GMT Received: from smtpav02.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 20CC35805C; Thu, 16 Jan 2025 11:16:52 +0000 (GMT) Received: from smtpav02.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 47C4E5805A; Thu, 16 Jan 2025 11:16:48 +0000 (GMT) Received: from [9.171.16.18] (unknown [9.171.16.18]) by smtpav02.dal12v.mail.ibm.com (Postfix) with ESMTP; Thu, 16 Jan 2025 11:16:47 +0000 (GMT) Message-ID: <0b4052bb-5ad3-42a3-a81e-e81d722036b7@linux.ibm.com> Date: Thu, 16 Jan 2025 16:46:46 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] mm/swap.c: Enable promotion of unmapped MGLRU page cache pages To: Gregory Price Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yu Zhao , Ritesh Harjani , "Aneesh Kumar K . V" , Matthew Wilcox , David Hildenbrand , Huang Ying , Johannes Weiner References: <20250115120625.3785-1-donettom@linux.ibm.com> Content-Language: en-US From: Donet Tom In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 51WMpZ8qak11Zd_xh7rh3StnSOtGnKnj X-Proofpoint-ORIG-GUID: lHvSRRx1NjQGfb35k9cq4TSs-qrPM-P5 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-16_04,2025-01-16_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 impostorscore=0 spamscore=0 malwarescore=0 lowpriorityscore=0 mlxscore=0 suspectscore=0 priorityscore=1501 bulkscore=0 mlxlogscore=999 clxscore=1015 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501160082 X-Rspamd-Queue-Id: 18CB316000F X-Stat-Signature: qpupd47r1rring4xcjri41wfa7bibiag X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1737026220-661041 X-HE-Meta: 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 dOzFnh/r bYQVRWKZNJxCSUUQ6U9wEY0ILBzJtctzpmKyYpJwzQGUKv+qg/ucQlEqetq+06eb70JAhOLnk6xsHV/OV7H2TutJENcfMjKAZQ1YUjLM2f8GIBpFOveNdarLiJDE8zgPe03BcGostV8/nR8U1XvXactBQYOgZUjGGFVmC4ERB+nfD8BVekXCt3ZBQ0BxgYNMj4nb/4oGzhzpmuwNnwYYV1P/ro59gxGtsXoFfvEISPjH6M+XL921QW6rEdYsrSoBwzAH6D+LsygGMHNlCbqgPBKoCAvx6MZpLyzx17Vtavi2R3AK1xTy1Ufm8169dV4U/WaGq0htQvyNabTpEUhd+Fa09hr3GbbrNX5Lnyadce0ZcbzL4cFxlrQyjcrGW/LESa6tIP8dd69MweH31CoUWcitre/m06qrLNieg 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: List-Subscribe: List-Unsubscribe: On 1/15/25 21:39, Gregory Price wrote: > On Wed, Jan 15, 2025 at 06:06:25AM -0600, Donet Tom wrote: > ... snip ... > > Thank you for taking the time to do this, I don't have enough background > with MGLRU to have done this quickly. I'll pull this onto my branch and > carry it if you don't mind so we can keep things tracked. > > I'll send you an updated RFC before i send out v4 and add appropriate tags. Sure. Thank you. > >> This difference also impacts read latency: >> >> For MGLRU, the first read shows higher latency due to the combined >> overhead of accessing a lower tier and performing promotion. >> >> For LRU, the first 3–4 reads typically exhibit lower latency since >> promotion does not occur immediately. >> > Do you have a thought on a good test we can use to compare these > strategies? I am also thinking on the same. I will come back with some tests which can compare these strategies. > > We decided against promotion on first-access because there are many > easy-to-imagine scenarios where that will clearly harm performance. Yes, I agree. After the first access, it gets promoted, but if those pages are not accessed afterward, it will become an overhead. I will check if we have any mechanism to restrict it. > > We're planning to do some workload testing soon so we can get actual > benefit numbers. Could you please let me know what workload you are planning? I can try it on my system as well. > >> +promo_candid: >> + if (!folio_test_isolated(folio) && >> + (sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && >> + numa_pagecache_promotion_enabled) { > I am considering putting this in some inline wrapper with some likely() > tags to clean this up a bit and optimize the fall-through cases since > i've seen some measurable differences when left as-is. Sounds good to me. > > Thoughts on this are welcome > >> + memcg = folio_memcg(folio); >> + if (memcg) { > Also curious, why only promote when the folio is a member of a memcg? I missed non memcg pages. I will send a V2 with that. ~Donet > > ~Gregory