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Fri, 28 Feb 2025 22:05:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id qvijGSMzwmdOQwAAD6G6ig (envelope-from ); Fri, 28 Feb 2025 22:05:23 +0000 Message-ID: Date: Fri, 28 Feb 2025 23:05:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/list_lru: allocate on first insert instead of allocation Content-Language: en-US From: Vlastimil Babka To: Johannes Weiner , Jingxiang Zeng Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, david@redhat.com, muchun.song@linux.dev, chengming.zhou@linux.dev, kasong@tencent.com, lkp@intel.com, Zeng Jingxiang References: <20250228113836.136318-1-jingxiangzeng.cas@gmail.com> <20250228163437.GA120597@cmpxchg.org> Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 3020BC0015 X-Stat-Signature: 3nkmixz69hd8r8uwmjgbnctofk3nnx6j X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1740780326-567191 X-HE-Meta: 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 FrvviqlU DfLPKcoo91hxbEpCq2c4BU6kBON6EvnMgg/pTncLmdDbXNH8ad176+L7+1cSM4fwkcbYknD7vIiKPg968w3eJ76k8f8XiIKEa9neoLsWjcSBilceepXGArdSS6AGyIzbXK3CJFBjNcz37yE7oQ/uq/3YmPttzCnjbUOHQOlbyJtUH8OCicUBtbIXWkyswLgUKeM2lEeVzqBjE3VqufvlBs5/hItaN3dxaztHbzkS4yFqH3vrYiGFGBCiVWDPzxXsc3bhzAGGmwIiJqZh27w6R7VHTctunkdLQqa9+UoO/YVZtbge0K5c9m+V2U3O2S67b1PhYYsxxLaLpVNgyYMH3t6c0SnSPSK1LDC4bkdVZD3EFI3M04jreqs2EqXR+YpP9qohOsw9lZsHbCQf2OoZP06mSdA== 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 2/28/25 18:18, Vlastimil Babka wrote: > On 2/28/25 17:34, Johannes Weiner wrote: >> On Fri, Feb 28, 2025 at 07:38:36PM +0800, Jingxiang Zeng wrote: >>> @@ -84,6 +86,9 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg, >>> spin_unlock_irq(&l->lock); >>> else >>> spin_unlock(&l->lock); >>> + } else { >>> + if (!memcg_list_lru_alloc(memcg, lru)) >>> + goto again; >>> } >> >> Unfortunately, you can't do allocations from this path :( >> >> list_lru_add() is called from many places with spinlocks, rcu locks >> etc. held. > > Aww, I was hoping we'd get rid of all the plumbing of lru through the slab > allocator. > But maybe we could, anyway? In __memcg_slab_post_alloc_hook() AFAICS the > only part that lru handling reuses is the objcg pointer. Moving the code to > kmem_cache_alloc_lru() would mean just another current_obj_cgroup() lookup > and that's not that expensive in the likely() cases, or is it? At the time it was introduced by commit 88f2ef73fd66 ("mm: introduce kmem_cache_alloc_lru") there was get_obj_cgroup_from_current() which seems much more involved - looking up memcg first, then ojbcg from that, with a obj_cgroup_tryget(). The tradeoff might be different today and not warrant the lru parameter anymore.