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[66.111.4.224]) by mx.google.com with ESMTPS id c11si6742618qko.203.2019.04.11.01.27.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Apr 2019 01:27:32 -0700 (PDT) Received-SPF: neutral (google.com: 66.111.4.224 is neither permitted nor denied by domain of penberg@iki.fi) client-ip=66.111.4.224; Authentication-Results: mx.google.com; dkim=pass header.i=@messagingengine.com header.s=fm2 header.b=JigCMARg; spf=neutral (google.com: 66.111.4.224 is neither permitted nor denied by domain of penberg@iki.fi) smtp.mailfrom=penberg@iki.fi; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=iki.fi Received: from compute4.internal (compute4.nyi.internal [10.202.2.44]) by mailnew.nyi.internal (Postfix) with ESMTP id 663755A4B; Thu, 11 Apr 2019 04:27:32 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute4.internal (MEProxy); Thu, 11 Apr 2019 04:27:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm2; bh=8u2aEsZLEcR3+NjWzB2WQbH67+zA4PHcHkWEVgf17 q8=; b=JigCMARgrDNIum5VLN/vsLwM+7b/HmaMjhOl1gQgI1DMsfEtQqx1Lp7V+ I1LKTlANOniVThkARVNXhfzle/8SlP4NfgNpkJTg8HIUvDryMe5NqsIfP9ZPnBpj cm1QmSfLlvmamSRIQ/7QJZz9c2WKBAmZllGZvlhijoyOLXwG4O/QleI0bnmAf9A0 dyZxq7AqyAL/j9MWFghdSCXxSmZI/oYZ8rkzytD1JbwlP5znLwquo9CdX+c+ZrIm FKIh6n+Qcvb9+OW9or4cHefL1Gop8IEXaP66p+iBv/6SWUMb4mx+12wNXyutZi1P qZO3AK7K/isKWsgBGqfEZn5IdM98Q== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduuddrudelgddtgecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdpuffrtefokffrpgfnqfghnecu uegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenuc fjughrpefuvfhfhffkffgfgggjtgfgsehtjeertddtfeejnecuhfhrohhmpefrvghkkhgr ucfgnhgsvghrghcuoehpvghnsggvrhhgsehikhhirdhfiheqnecukfhppeekledrvdejrd effedrudejfeenucfrrghrrghmpehmrghilhhfrhhomhepphgvnhgsvghrghesihhkihdr fhhinecuvehluhhsthgvrhfuihiivgeptd X-ME-Proxy: Received: from [192.168.1.104] (89-27-33-173.bb.dnainternet.fi [89.27.33.173]) by mail.messagingengine.com (Postfix) with ESMTPA id 2B2E01030F; Thu, 11 Apr 2019 04:27:28 -0400 (EDT) Subject: Re: [PATCH 0/1] mm: Remove the SLAB allocator To: Michal Hocko , "Tobin C. Harding" Cc: Vlastimil Babka , "Tobin C. Harding" , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Tejun Heo , Qian Cai , Linus Torvalds , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman References: <20190410024714.26607-1-tobin@kernel.org> <20190410081618.GA25494@eros.localdomain> <20190411075556.GO10383@dhcp22.suse.cz> From: Pekka Enberg Message-ID: <262df687-c934-b3e2-1d5f-548e8a8acb74@iki.fi> Date: Thu, 11 Apr 2019 11:27:26 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190411075556.GO10383@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit 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: Hi, On 4/11/19 10:55 AM, Michal Hocko wrote: > Please please have it more rigorous then what happened when SLUB was > forced to become a default This is the hard part. Even if you are able to show that SLUB is as fast as SLAB for all the benchmarks you run, there's bound to be that one workload where SLUB regresses. You will then have people complaining about that (rightly so) and you're again stuck with two allocators. To move forward, I think we should look at possible *pathological* cases where we think SLAB might have an advantage. For example, SLUB had much more difficulties with remote CPU frees than SLAB. Now I don't know if this is the case, but it should be easy to construct a synthetic benchmark to measure this. For example, have a userspace process that does networking, which is often memory allocation intensive, so that we know that SKBs traverse between CPUs. You can do this by making sure that the NIC queues are mapped to CPU N (so that network softirqs have to run on that CPU) but the process is pinned to CPU M. It's, of course, worth thinking about other pathological cases too. Workloads that cause large allocations is one. Workloads that cause lots of slab cache shrinking is another. - Pekka