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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B3816C433EF for ; Thu, 14 Oct 2021 08:50:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 90981610EA for ; Thu, 14 Oct 2021 08:50:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229988AbhJNIwm (ORCPT ); Thu, 14 Oct 2021 04:52:42 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:13738 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229551AbhJNIwk (ORCPT ); Thu, 14 Oct 2021 04:52:40 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4HVNNm3srgzWrbl; Thu, 14 Oct 2021 16:48:56 +0800 (CST) Received: from dggpemm500002.china.huawei.com (7.185.36.229) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Thu, 14 Oct 2021 16:50:34 +0800 Received: from [10.174.178.178] (10.174.178.178) by dggpemm500002.china.huawei.com (7.185.36.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Thu, 14 Oct 2021 16:50:34 +0800 Message-ID: <9d6f8c72-8bcb-39ce-baa8-00e42e5e97da@huawei.com> Date: Thu, 14 Oct 2021 16:50:16 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.0.3 Subject: Re: [PATCH] mm/vmalloc: fix numa spreading for large hash tables To: Andrew Morton CC: , , , , , References: <20210928121040.2547407-1-chenwandun@huawei.com> <20210928153302.f87537b5faac8637c3c5eb53@linux-foundation.org> From: Chen Wandun In-Reply-To: <20210928153302.f87537b5faac8637c3c5eb53@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.178] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500002.china.huawei.com (7.185.36.229) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/9/29 6:33, Andrew Morton 写道: > On Tue, 28 Sep 2021 20:10:40 +0800 Chen Wandun wrote: > >> Eric Dumazet reported a strange numa spreading info in [1], and found >> commit 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings") introduced >> this issue [2]. >> >> Dig into the difference before and after this patch, page allocation has >> some difference: >> >> before: >> alloc_large_system_hash >> __vmalloc >> __vmalloc_node(..., NUMA_NO_NODE, ...) >> __vmalloc_node_range >> __vmalloc_area_node >> alloc_page /* because NUMA_NO_NODE, so choose alloc_page branch */ >> alloc_pages_current >> alloc_page_interleave /* can be proved by print policy mode */ >> >> after: >> alloc_large_system_hash >> __vmalloc >> __vmalloc_node(..., NUMA_NO_NODE, ...) >> __vmalloc_node_range >> __vmalloc_area_node >> alloc_pages_node /* choose nid by nuam_mem_id() */ >> __alloc_pages_node(nid, ....) >> >> So after commit 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings"), >> it will allocate memory in current node instead of interleaving allocate >> memory. >> >> [1] >> https://lore.kernel.org/linux-mm/CANn89iL6AAyWhfxdHO+jaT075iOa3XcYn9k6JJc7JR2XYn6k_Q@mail.gmail.com/ >> >> [2] >> https://lore.kernel.org/linux-mm/CANn89iLofTR=AK-QOZY87RdUZENCZUT4O6a0hvhu3_EwRMerOg@mail.gmail.com/ >> >> Fixes: 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings") >> Reported-by: Eric Dumazet >> Signed-off-by: Chen Wandun > > This seems like it could cause significant performance regressions in > some situations? Yes，I indeed will cause some performance regressions, I will send a optimization patch based on this patch. > > If "yes" then wouldn't a cc:stable be appropriate? And some (perhaps > handwavy) quantification of the slowdown would help people understand > why we're recommending a backport. > > If "no" then why the heck do we have that feature in there anyway ;) > > . >