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 2D7D4C43334 for ; Thu, 30 Jun 2022 02:30:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C22F58E0003; Wed, 29 Jun 2022 22:30:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BD2948E0001; Wed, 29 Jun 2022 22:30:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AC1F48E0003; Wed, 29 Jun 2022 22:30:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 9D3818E0001 for ; Wed, 29 Jun 2022 22:30:11 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id 7F9AB60388 for ; Thu, 30 Jun 2022 02:30:11 +0000 (UTC) X-FDA: 79633322622.16.2DDE3EE Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf07.hostedemail.com (Postfix) with ESMTP id F25554003F for ; Thu, 30 Jun 2022 02:30:10 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 31DB9B827DB; Thu, 30 Jun 2022 02:30:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7CDFDC34114; Thu, 30 Jun 2022 02:30:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1656556208; bh=NnybmbeAGGn2R9XqSjtu72EBzlcQuCDFvjoFj0kGor8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=zokvkdPOolcqpwXgwOO/60AcLiBNevbBePZMYXAwx2dg3TDmLQtANAexZYqgs8MFY gKJOWFU/IKaw57VgNqZHSY9oxsLGBjaJvTvSuWnqz+gQtBdbreUCBjtVUzT832/cF6 NUXTZ9cUQpPwBhnvJyNOkDaDUcqJFNkpZS9o2Jkw= Date: Wed, 29 Jun 2022 19:30:06 -0700 From: Andrew Morton To: Feng Tang Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, dave.hansen@intel.com, Joerg Roedel , Robin Murphy Subject: Re: [RFC PATCH] mm/slub: enable debugging memory wasting of kmalloc Message-Id: <20220629193006.77e9f071a5940e882c459cdd@linux-foundation.org> In-Reply-To: <20220630014715.73330-1-feng.tang@intel.com> References: <20220630014715.73330-1-feng.tang@intel.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656556211; a=rsa-sha256; cv=none; b=bc9GClRs97ldo1eNLLkE40medVaxv00KMO55DPgloxUBqtVAulo8tEcq7HM7Yz2QSF7sL8 lwfUNBoALrG4ghZkGGRKTKMie9Ym1KWJW+Rs0Q1bCy85o2iFztLD+q4hYLA8y9maCrD4EF AZzcDVQHQq8MZhatsJfFV10EMUjzAKQ= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=zokvkdPO; dmarc=none; spf=pass (imf07.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656556211; 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=8703lMIOkmz7Ir1AX7wX1GGc6PqBlELEAATrKLaVPbI=; b=CNY3a1n7PAn0I7AKo4uR3Nh5WbRz3Hj7B0v0YO2b5pwwtQgHn63+sFFEK/Hwfyr8g0VtjQ hrtnqYA/t8bWhKQCV8xmsa/swjUDwa02owhOQG3GxOvAEolDWgsILBp5g9cgJKCjyd2dnM eCWDZWlaneU0xbocG8hJWkT1+qVnybc= X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: F25554003F Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=zokvkdPO; dmarc=none; spf=pass (imf07.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspam-User: X-Stat-Signature: 8npaxmf1jpir5fniaa6ixowkwprxe4wg X-HE-Tag: 1656556210-95286 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: On Thu, 30 Jun 2022 09:47:15 +0800 Feng Tang wrote: > kmalloc's API family is critical for mm, with one shortcoming that > its object size is fixed to be power of 2. When user requests memory > for '2^n + 1' bytes, actually 2^(n+1) bytes will be allocated, so > in worst case, there is around 50% memory space waste. > > We've met a kernel boot OOM panic, and from the dumped slab info: > > [ 26.062145] kmalloc-2k 814056KB 814056KB > > >From debug we found there are huge number of 'struct iova_magazine', > whose size is 1032 bytes (1024 + 8), so each allocation will waste > 1016 bytes. Though the issue is solved by giving the right(bigger) > size of RAM, it is still better to optimize the size (either use > a kmalloc friendly size or create a dedicated slab for it). Well that's nice, and additional visibility is presumably a good thing. But what the heck is going on with iova_magazine? Is anyone looking at moderating its impact?