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 5FC04C433EF for ; Fri, 28 Jan 2022 19:29:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350943AbiA1T3d (ORCPT ); Fri, 28 Jan 2022 14:29:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56132 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232590AbiA1T3c (ORCPT ); Fri, 28 Jan 2022 14:29:32 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 480B6C061714 for ; Fri, 28 Jan 2022 11:29:32 -0800 (PST) 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 dfw.source.kernel.org (Postfix) with ESMTPS id D98EF61D42 for ; Fri, 28 Jan 2022 19:29:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E8977C340E7; Fri, 28 Jan 2022 19:29:29 +0000 (UTC) Date: Fri, 28 Jan 2022 19:29:26 +0000 From: Catalin Marinas To: Lang Yu Cc: linux-mm@kvack.org, David Hildenbrand , Oscar Salvador , linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH v2] mm/kmemleak: Avoid scanning potential huge holes Message-ID: References: <20211108140029.721144-1-lang.yu@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211108140029.721144-1-lang.yu@amd.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 08, 2021 at 10:00:29PM +0800, Lang Yu wrote: > When using devm_request_free_mem_region() and devm_memremap_pages() > to add ZONE_DEVICE memory, if requested free mem region's end pfn > were huge(e.g., 0x400000000), the node_end_pfn() will be also huge > (see move_pfn_range_to_zone()). Thus it creates a huge hole between > node_start_pfn() and node_end_pfn(). > > We found on some AMD APUs, amdkfd requested such a free mem region > and created a huge hole. In such a case, following code snippet was > just doing busy test_bit() looping on the huge hole. > > for (pfn = start_pfn; pfn < end_pfn; pfn++) { > struct page *page = pfn_to_online_page(pfn); > if (!page) > continue; > ... > } > > So we got a soft lockup: > > watchdog: BUG: soft lockup - CPU#6 stuck for 26s! [bash:1221] > CPU: 6 PID: 1221 Comm: bash Not tainted 5.15.0-custom #1 > RIP: 0010:pfn_to_online_page+0x5/0xd0 > Call Trace: > ? kmemleak_scan+0x16a/0x440 > kmemleak_write+0x306/0x3a0 > ? common_file_perm+0x72/0x170 > full_proxy_write+0x5c/0x90 > vfs_write+0xb9/0x260 > ksys_write+0x67/0xe0 > __x64_sys_write+0x1a/0x20 > do_syscall_64+0x3b/0xc0 > entry_SYSCALL_64_after_hwframe+0x44/0xae > > I did some tests with the patch. > > (1) amdgpu module unloaded > > before the patch: > > real 0m0.976s > user 0m0.000s > sys 0m0.968s > > after the patch: > > real 0m0.981s > user 0m0.000s > sys 0m0.973s > > (2) amdgpu module loaded > > before the patch: > > real 0m35.365s > user 0m0.000s > sys 0m35.354s > > after the patch: > > real 0m1.049s > user 0m0.000s > sys 0m1.042s > > v2: > - Only scan pages belonging to the zone.(David Hildenbrand) > - Use __maybe_unused to make compilers happy. > > Signed-off-by: Lang Yu Acked-by: Catalin Marinas