From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A6375C4167B for ; Mon, 4 Dec 2023 08:30:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 402D76B0272; Mon, 4 Dec 2023 03:30:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3B2676B0273; Mon, 4 Dec 2023 03:30:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2A20B6B0275; Mon, 4 Dec 2023 03:30:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 1B99F6B0272 for ; Mon, 4 Dec 2023 03:30:44 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id E52FC16015A for ; Mon, 4 Dec 2023 08:30:43 +0000 (UTC) X-FDA: 81528464766.06.8E6F274 Received: from out-185.mta1.migadu.com (out-185.mta1.migadu.com [95.215.58.185]) by imf02.hostedemail.com (Postfix) with ESMTP id C94B280008 for ; Mon, 4 Dec 2023 08:30:41 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=H7Xe+6ul; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf02.hostedemail.com: domain of chengming.zhou@linux.dev designates 95.215.58.185 as permitted sender) smtp.mailfrom=chengming.zhou@linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1701678642; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=9FCmOUDEhk/C/p/K392zgD3slK3uNuip9FSardg1Z7w=; b=m/2IaT/Dx+A+EQJACGwz8Ftq42UBgW8ENod73VyWkdWFUhvmE0XOEgfFxTN5/yBG0ByKmo DAL3mfWSnyE1ynGvCRG5FEFktMDt2Hqd9LfvcY9TlgWC6W7yTaF+fuznBrPFy0/+MQWV5U hhLTAg92aIUtm9kkur34RGQQFIKWgLE= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=H7Xe+6ul; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf02.hostedemail.com: domain of chengming.zhou@linux.dev designates 95.215.58.185 as permitted sender) smtp.mailfrom=chengming.zhou@linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1701678642; a=rsa-sha256; cv=none; b=m7SjrkfdySMHPl+H11S5dNIJ6egMxAobEamZFfGErLzRsT87uUxe0SfpgkleLovjpvctvo kFntf1oRZxM7K2aUdy/eH9CCHERB3YA+QJLSo+EbHix4Otm3j65VISCq6ufr8BTh4M7Pye 7x5A9CwSF9bOCMi3Zo1JZxruQb0QrIE= Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1701678639; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9FCmOUDEhk/C/p/K392zgD3slK3uNuip9FSardg1Z7w=; b=H7Xe+6ulWDPhZDnQCByRmYdIpY2aXt0AEa5eVX33L9yORgJy4M/sF0isMJ8ajiLMYY0dC8 +2DHQXuNPGb+doz5220ARXX7sOC6WL8kU5ft2JaRXcjkDC6CcHLAQojNz54+Er26BkcAnQ UlwRCkMJY+fOVKmL8YnvcFgjGkxzxIU= Date: Mon, 4 Dec 2023 16:30:29 +0800 MIME-Version: 1.0 Subject: Re: [PATCH v8 1/6] list_lru: allows explicit memcg and NUMA node selection Content-Language: en-US To: Johannes Weiner , Nhat Pham Cc: Matthew Wilcox , akpm@linux-foundation.org, cerasuolodomenico@gmail.com, yosryahmed@google.com, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com, mhocko@kernel.org, roman.gushchin@linux.dev, shakeelb@google.com, muchun.song@linux.dev, chrisl@kernel.org, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, shuah@kernel.org References: <20231130194023.4102148-1-nphamcs@gmail.com> <20231130194023.4102148-2-nphamcs@gmail.com> <20231130203522.GC543908@cmpxchg.org> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Chengming Zhou In-Reply-To: <20231130203522.GC543908@cmpxchg.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: C94B280008 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 317848qrc11hoanjc1kmiokos3idj3f6 X-HE-Tag: 1701678641-338311 X-HE-Meta: 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 eHLs21ZB Cy8yfn0hgLsLVappoVSru/R1Xr3aCxvrafJAG3P10lKDJp3KI+/WBtRlPBimNzcSldfw7ebUH3V3D7dNGbEUljf44cmM60o7qCwcci9muIiNNKL5DHFY/hqq4jfo+TZllXo8UVmTOSDLr7WiLJcYF5JOm/5EXmvguIC3PVeXuWLJWBjLogOFYbx6G/lpHe0S2Lm0O6YpvAP/RzmENwJyH9xm/B3XAD2H01WCp2Di2utzMGiqv8ax75n8YsQ== 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 2023/12/1 04:35, Johannes Weiner wrote: > On Thu, Nov 30, 2023 at 12:07:41PM -0800, Nhat Pham wrote: >> On Thu, Nov 30, 2023 at 11:57 AM Matthew Wilcox wrote: >>> >>> On Thu, Nov 30, 2023 at 11:40:18AM -0800, Nhat Pham wrote: >>>> This patch changes list_lru interface so that the caller must explicitly >>>> specify numa node and memcg when adding and removing objects. The old >>>> list_lru_add() and list_lru_del() are renamed to list_lru_add_obj() and >>>> list_lru_del_obj(), respectively. >>> >>> Wouldn't it be better to add list_lru_add_memcg() and >>> list_lru_del_memcg() and have: >>> >>> +bool list_lru_del(struct list_lru *lru, struct list_head *item) >>> +{ >>> + int nid = page_to_nid(virt_to_page(item)); >>> + struct mem_cgroup *memcg = list_lru_memcg_aware(lru) ? >>> + mem_cgroup_from_slab_obj(item) : NULL; >>> + >>> + return list_lru_del_memcg(lru, item, nid, memcg); >>> +} >>> >>> Seems like _most_ callers will want the original versions and only >>> a few will want the explicit memcg/nid versions. No? >>> >> >> I actually did something along that line in earlier iterations of this >> patch series (albeit with poorer naming - __list_lru_add() instead of >> list_lru_add_memcg()). The consensus after some back and forth was >> that the original list_lru_add() was not a very good design (the >> better one was this new version that allows for explicit numa/memcg >> selection). So I agreed to fix it everywhere as a prep patch. >> >> I don't have strong opinions here to be completely honest, but I do >> think this new API makes more sense (at the cost of quite a bit of >> elbow grease to fix every callsites and extra reviewing). > > Maybe I can shed some light since I was pushing for doing it this way. > > The quiet assumption that 'struct list_head *item' is (embedded in) a > slab object that is also charged to a cgroup is a bit much, given that > nothing in the name or documentation of the function points to that. > > It bit us in the THP shrinker where that list head is embedded in a > tailpage (virt_to_page(page) is fun to debug). And it caused some > confusion in this case as well, where the zswap entry is a slab object > but not charged (the entry descriptor is not attractive for cgroup > accounting, only the backing memory it points to.) Hi, I have a question, maybe I missed something since I haven't read all the earlier versions. IIUC, the problem here is that "zswap_entry" has different memcg and node than the "page", so I wonder if we can just charge "zswap_entry" to the same memcg of the "page". Like we can do these when allocating the "zswap_entry": old_memcg = set_active_memcg(memcg) kmem_cache_alloc_lru(zswap_entry_cache, lru, gfp) set_active_memcg(old_memcg) The good points are: 1. "zswap_entry" is charged to the memcg of "page", which is more sensible? 2. We can reuse the kmem_cache_alloc_lru() interface, which makes code simpler since we don't need to manage list_lru_memcg by ourselves. 3. Maybe the new list_lru_add() and list_lru_del() are not needed anymore? Since the "zswap_entry" is of the same memcg and node with the "page". But don't know if THP shrinker still need it. Thanks! > > Yes, for most users - at least right now - the current assumption is > accurate. The thinking was just that if we do have to differentiate > callers now anyway, we might as well make the interface a bit more > self-documenting and harder to misuse going forward, even if it's a > bit more churn now. > >