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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF7C4C433F5 for ; Thu, 28 Apr 2022 20:19:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351720AbiD1UXI (ORCPT ); Thu, 28 Apr 2022 16:23:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57622 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233218AbiD1UXG (ORCPT ); Thu, 28 Apr 2022 16:23:06 -0400 Received: from mail-oi1-x22c.google.com (mail-oi1-x22c.google.com [IPv6:2607:f8b0:4864:20::22c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 370EFB1AB0 for ; Thu, 28 Apr 2022 13:19:51 -0700 (PDT) Received: by mail-oi1-x22c.google.com with SMTP id 12so6493785oix.12 for ; Thu, 28 Apr 2022 13:19:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=mP2dZIg49i0nx6hN/uSu0sPbA4AamYLAjMK1jPC0V3w=; b=S7y8kcdcygzpAizHWfOc2pPFnbYhQfyNg4+kSYrCKxGfkJSzDYH5ZTPwbyVcd5KEKp 5M9o2TjpjxJX7gUd8AkFHeef71gPMrfTxgucCazyOIleU5BPkTzFAGD00s1UwvaKj3Z9 PJr+7847FK6QFfMOIm68Yad2EMWziKPo+oekA+3r4qYJj5I9VmKuUZIZcA+wERAylSmR gvY0swhDrGr8iFuFUnp8wHV3wlz+TJ1aHo4Hmjxnh2gxKZ+PFZbFXIaa0l46QvU4+mch deje8jLXAHdreTQZjo16PIBxX23X+3F6mIMlOMEUsvR/EyrQEHN1Wfmrc0dFiNRUvPrq +zxw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=mP2dZIg49i0nx6hN/uSu0sPbA4AamYLAjMK1jPC0V3w=; b=xx/agnabvsifgp9yQcpbk8k4MUXTzIfk8yIJPebk2eWhF7vuiuPhN9rsY76qcR24xn OnWBkA1pzNEKhEyIQDICTlWoY88vUtmDn1g/rhCCspoeqhbx8ObHHNA30fPN/vjAmwCe kArUavI5R/jsfXeoRQ4MyIQQA8EOatCXqPP0fxmhgOiEO7GhHMPU9L1gZ/e4JiSmBTXv 4R1SKxw/3vQDTMC/9iKDeqxxk5CjWael6EYCP5UpFanxlxT4W0wEbcC8ZEaukJNCFXRL ynb0RB2ddvV3pJSm6MA7NDrEhoAwJkxGnX8eyMhR3K//u40j09qekaXlx3ZxXKVxUkWV YNQA== X-Gm-Message-State: AOAM531RM0pEFn2DHRkONj/zqc3tRVr22XJRQoWu3hb6SjbKRlkWwcVV Fk/yXUdxR04xQ0p3q301eNY= X-Google-Smtp-Source: ABdhPJwD9CTmFzKeUdj2tI/XXpF/h3vLn0q0cKXhcXLsGZ6knga/3qdO3GVT45ODKBxnhB57vLnDGA== X-Received: by 2002:a05:6808:1244:b0:2f9:e450:4bc4 with SMTP id o4-20020a056808124400b002f9e4504bc4mr16771429oiv.290.1651177190506; Thu, 28 Apr 2022 13:19:50 -0700 (PDT) Received: from server.roeck-us.net ([2600:1700:e321:62f0:329c:23ff:fee3:9d7c]) by smtp.gmail.com with ESMTPSA id bt30-20020a0568201a9e00b0035ea84682b9sm459598oob.45.2022.04.28.13.19.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Apr 2022 13:19:49 -0700 (PDT) Sender: Guenter Roeck Date: Thu, 28 Apr 2022 13:19:47 -0700 From: Guenter Roeck To: Liam Howlett Cc: "maple-tree@lists.infradead.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Yu Zhao Subject: Re: [PATCH v8 23/70] mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap() Message-ID: <20220428201947.GA1912192@roeck-us.net> References: <20220426150616.3937571-1-Liam.Howlett@oracle.com> <20220426150616.3937571-24-Liam.Howlett@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220426150616.3937571-24-Liam.Howlett@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 26, 2022 at 03:06:35PM +0000, Liam Howlett wrote: > From: "Liam R. Howlett" > > Avoid allocating a new VMA when it a vma modification can occur. When a > brk() can expand or contract a VMA, then the single store operation will > only modify one index of the maple tree instead of causing a node to split > or coalesce. This avoids unnecessary allocations/frees of maple tree > nodes and VMAs. > > Move some limit & flag verifications out of the do_brk_flags() function to > use only relevant checks in the code path of bkr() and vm_brk_flags(). > > Set the vma to check if it can expand in vm_brk_flags() if extra criteria > are met. > > Drop userfaultfd from do_brk_flags() path and only use it in > vm_brk_flags() path since that is the only place a munmap will happen. > > Signed-off-by: Liam R. Howlett A build failure seen when building ppc64:corenet64_smp_defconfig also biscects to this patch. mm/mmap.c: In function 'do_brk_flags': mm/mmap.c:2908:17: error: implicit declaration of function 'khugepaged_enter_vma_merge'; did you mean 'khugepaged_enter_vma'? It appears that this is later fixed, but it hurts bisectability (and prevents me from finding the actual build failure in linux-next when trying to build corenet64_smp_defconfig). While looking into the patch, I noticed the following. [ ... ] > @@ -2773,30 +2888,52 @@ static int do_brk_flags(unsigned long addr, unsigned long len, > if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT)) > return -ENOMEM; > > out: > perf_event_mmap(vma); > mm->total_vm += len >> PAGE_SHIFT; > @@ -2807,18 +2944,21 @@ static int do_brk_flags(unsigned long addr, unsigned long len, > validate_mm_mt(mm); > return 0; > > -no_vma_link: > vm_area_free(vma); That really looks wrong. vm_area_free(vma) can not be reached after this patch has been applied. Guenter > +vma_alloc_fail: > + vm_unacct_memory(len >> PAGE_SHIFT); > return -ENOMEM; > } >