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[209.85.208.170]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5334ea294e0sm183692e87.12.2024.08.22.02.53.39 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Aug 2024 02:53:39 -0700 (PDT) Received: by mail-lj1-f170.google.com with SMTP id 38308e7fff4ca-2ef2c56d9dcso5288921fa.2 for ; Thu, 22 Aug 2024 02:53:39 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCVP6VsWx8apfCa2vyZmZic60UlIRQxhUNtdS1zLY0Iq8x7AigDTJXNK8oQfocTuYCbr8vJxWZuu9Q==@kvack.org X-Received: by 2002:a05:651c:221b:b0:2ef:2b06:b686 with SMTP id 38308e7fff4ca-2f3f8833529mr43486231fa.17.1724320419189; Thu, 22 Aug 2024 02:53:39 -0700 (PDT) MIME-Version: 1.0 References: <59e90825-4efa-4384-8286-06c0235304dc@redhat.com> <4df58ef1-b379-484a-aa5d-ef77a1200c63@redhat.com> In-Reply-To: <4df58ef1-b379-484a-aa5d-ef77a1200c63@redhat.com> From: Linus Torvalds Date: Thu, 22 Aug 2024 17:53:22 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 0/4] mm: clarify nofail memory allocation To: David Hildenbrand Cc: Michal Hocko , Barry Song <21cnbao@gmail.com>, Yafang Shao , akpm@linux-foundation.org, linux-mm@kvack.org, 42.hyeyoo@gmail.com, cl@linux.com, hailong.liu@oppo.com, hch@infradead.org, iamjoonsoo.kim@lge.com, penberg@kernel.org, rientjes@google.com, roman.gushchin@linux.dev, urezki@gmail.com, v-songbaohua@oppo.com, vbabka@suse.cz, virtualization@lists.linux.dev Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: DF6E1160002 X-Stat-Signature: ah3ax55nskeakdmfo78zddismcaz843t X-Rspam-User: X-HE-Tag: 1724320422-993935 X-HE-Meta: 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 ebTKqOcN 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 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 Thu, 22 Aug 2024 at 17:43, David Hildenbrand wrote: > > So on the buddy level, that might mean that we limit it to a single > page, Actually, for many SLUB allocations, you probably do have to accept the small orders - the slab caches are often two or four pages. For example, a kmalloc(256) is an order-1 allocation on a buddy level from a quick look at /proc/slabinfo. So it's not necessarily only single pages. We do handle small orders. But it gets exponentially harder, so it really is just the small orders that work. Looks like slub will use up to order-3. That smells like an off-by-one to me (I thought we made 0-2 be the "cheap" orders, but maybe I'm just wrong), but it probably is still acceptable. Linus