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 5E0AAC02198 for ; Fri, 14 Feb 2025 18:28:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EA8C1280009; Fri, 14 Feb 2025 13:28:14 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E3150280002; Fri, 14 Feb 2025 13:28:14 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CD329280009; Fri, 14 Feb 2025 13:28:14 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id B3361280002 for ; Fri, 14 Feb 2025 13:28:14 -0500 (EST) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 6AD53A0810 for ; Fri, 14 Feb 2025 18:28:14 +0000 (UTC) X-FDA: 83119384908.07.391E559 Received: from gentwo.org (gentwo.org [62.72.0.81]) by imf18.hostedemail.com (Postfix) with ESMTP id BF78D1C0004 for ; Fri, 14 Feb 2025 18:28:12 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=gentwo.org header.s=default header.b=KxzOWGoV; spf=pass (imf18.hostedemail.com: domain of cl@gentwo.org designates 62.72.0.81 as permitted sender) smtp.mailfrom=cl@gentwo.org; dmarc=pass (policy=reject) header.from=gentwo.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1739557692; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=PvPuFswuZjHqFCVRfTTP/fywLLVdnOpi5bELowe+3yg=; b=ZfClioQzVeqGzYtfDG9tFY7+Gnnk+1+oiT8mTSRkpSO4e+OocDAbh1wKVzbSdtTNMz6I1z pT259Kypz2wIPS3IQ2fLXGK6hXmJsKPkFy7GDlmdchREWPfLRFeRL6KrW7nsA1XtB77Bgv OZ7b1xk5ta1h1cexBZBy1OHEeslOgWQ= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=gentwo.org header.s=default header.b=KxzOWGoV; spf=pass (imf18.hostedemail.com: domain of cl@gentwo.org designates 62.72.0.81 as permitted sender) smtp.mailfrom=cl@gentwo.org; dmarc=pass (policy=reject) header.from=gentwo.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1739557692; a=rsa-sha256; cv=none; b=KmlVJ5A+12u/gnoR7fP4Obtco7GVUPg7nfrgoqb0x92ECcHvLVIiQ3FiTeDZn9uXZNwf5A bZ0aowba71VAIdD9oBH1rJpUQoY+vRICF2faxgtJAFHb3vStCwUJNCNhLbip2VfbUvhnX2 iW586bhxiNMOWnXuWxPVdyRmPqGd8NQ= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gentwo.org; s=default; t=1739557691; bh=tsQoV1mQsqNq6InM3wdlxDCaycM+dXDK7QEIVPJAyVo=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=KxzOWGoVA3Lr0vtA4YT+TzVPhfYb9BsfsHOyVp+5PPESOR3vMPic7JfF32YCtAJUx nTjuVhfNs/Gh2B5SWRc+NGWWlsv58yJx7PNsPKzOQN2YTI9lglVzQ1d6cWmONjCmHQ tQXqy3+Xc+RjB2zzg8hn/5bmUPApiYFbkkhLxSzY= Received: by gentwo.org (Postfix, from userid 1003) id B29CE40A17; Fri, 14 Feb 2025 10:28:11 -0800 (PST) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id B1984400C6; Fri, 14 Feb 2025 10:28:11 -0800 (PST) Date: Fri, 14 Feb 2025 10:28:11 -0800 (PST) From: "Christoph Lameter (Ampere)" To: Vlastimil Babka cc: Suren Baghdasaryan , "Liam R. Howlett" , David Rientjes , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, maple-tree@lists.infradead.org, Sebastian Andrzej Siewior , Alexei Starovoitov Subject: Re: [PATCH RFC v2 00/10] SLUB percpu sheaves In-Reply-To: <20250214-slub-percpu-caches-v2-0-88592ee0966a@suse.cz> Message-ID: References: <20250214-slub-percpu-caches-v2-0-88592ee0966a@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: BF78D1C0004 X-Stat-Signature: j6t7c8hi1dxf51n4uq6nhixaak5qzgqc X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1739557692-482217 X-HE-Meta: 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 fLa8rOXk b6j1ytozCX3+h4RxzY66+onM98wEARIkPAzRqSCd0v2LqVn4HGassPOvywxAwnXXwwlD0/czVWyCOPRu7lAvfTlflleJme8EqXIHkQdLskZO2Tatfa7RiAbETzAt4XjCgF8rUR8iKK0XQMFIQ6JtgdQnpaow31g18ylSwFaotl03491dVz8J3waPnekOG3rz4AGIeH37l89DMkmVY7hdZWriKm32AqMMuoUf7FEKh6T60XcZlVOABBR96f5LdcWBcX6cOjTHEkfyISJgiQt5d5okZaASqtR+BYRELRqIVhl48laN9kHF73EKXNDeCnPKYy2dAvIK1ui31aD7S51JUf7LaIw== 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 Fri, 14 Feb 2025, Vlastimil Babka wrote: > - Cheaper fast paths. For allocations, instead of local double cmpxchg, > after Patch 5 it's preempt_disable() and no atomic operations. Same for > freeing, which is normally a local double cmpxchg only for a short > term allocations (so the same slab is still active on the same cpu when > freeing the object) and a more costly locked double cmpxchg otherwise. > The downside is the lack of NUMA locality guarantees for the allocated > objects. The local double cmpxchg is not an atomic instruction. For that it would need a lock prefix. The local cmpxchg is atomic vs an interrupt because the interrupt can only occur between instructions. That is true for any processor instruction. We use the fact that the cmpxchg does a RMV in one unbreakable instruction to ensure that interrupts cannot do evil things to the fast path.