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 0C4E8C4332F for ; Wed, 20 Apr 2022 18:28:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 55AEA6B0071; Wed, 20 Apr 2022 14:28:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 509266B0073; Wed, 20 Apr 2022 14:28:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3AB986B0074; Wed, 20 Apr 2022 14:28:18 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id 295426B0071 for ; Wed, 20 Apr 2022 14:28:18 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id DB4D260EEE for ; Wed, 20 Apr 2022 18:28:17 +0000 (UTC) X-FDA: 79378092234.13.179FB41 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf30.hostedemail.com (Postfix) with ESMTP id C895C8001F for ; Wed, 20 Apr 2022 18:28:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=T1t1cTSum3OzRMUjY8k+SNYpptc4cLa0jL7we78Ggyc=; b=GEPlYe+XYe3dHkUmdDio8B/BN6 +ikXU0KkvaMRv/XNsGUpfWuxTFJ76oGWO9rpd1tdhAehY5Qgwqgc7vAnYetBB2n0yIv3BYnjZuZU5 1eau5eyzqsO/Uif2KnpsaYjX/GJpAXn9zTK0f7ICSyOjlpY9r5mbjcvYzTDV8AdNKUxOAR28F+NJ8 tkg++xBYRcoMum3dt+K8yUA2PHrM3AVGXApvXYuk3c4KKLTI1E/ZZKtUP966BuR/ZIw07vJMEcdNn 2I3ZKzlzm+vBj4/WdA4aol5LzvRLUCCstV8r6Ev9CBBKTUh5g5SWYsCRA8YFCaEqL7OQViSSnjYfI ksG5l2ig==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nhF3f-00A38V-Ql; Wed, 20 Apr 2022 18:28:07 +0000 Date: Wed, 20 Apr 2022 11:28:07 -0700 From: Luis Chamberlain To: Song Liu Cc: Linus Torvalds , Alexei Starovoitov , Mike Rapoport , "Edgecombe, Rick P" , "linux-kernel@vger.kernel.org" , "bpf@vger.kernel.org" , "hch@infradead.org" , "ast@kernel.org" , "daniel@iogearbox.net" , "linux-mm@kvack.org" , "song@kernel.org" , Kernel Team , "pmladek@suse.com" , "akpm@linux-foundation.org" , "hpa@zytor.com" , "dborkman@redhat.com" , "edumazet@google.com" , "bp@alien8.de" , "mbenes@suse.cz" , "imbrenda@linux.ibm.com" , Davidlohr Bueso Subject: Re: [PATCH v4 bpf 0/4] vmalloc: bpf: introduce VM_ALLOW_HUGE_VMAP Message-ID: References: <88eafc9220d134d72db9eb381114432e71903022.camel@intel.com> <20220420020311.6ojfhcooumflnbbk@MacBook-Pro.local.dhcp.thefacebook.com> <3F75142B-3E87-4195-A026-3A7F1E595960@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3F75142B-3E87-4195-A026-3A7F1E595960@fb.com> X-Stat-Signature: 1kpaj6s4gr666ixi1ynsstmcnrpytf44 X-Rspam-User: Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=bombadil.20210309 header.b=GEPlYe+X; dmarc=fail reason="No valid SPF, DKIM not aligned (relaxed)" header.from=kernel.org (policy=none); spf=none (imf30.hostedemail.com: domain of mcgrof@infradead.org has no SPF policy when checking 198.137.202.133) smtp.mailfrom=mcgrof@infradead.org X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C895C8001F X-HE-Tag: 1650479294-930995 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 Wed, Apr 20, 2022 at 02:42:37PM +0000, Song Liu wrote: > For (b), we have seen direct map fragmentation causing visible > performance drop for our major services. This is the shadow > production benchmark, so it is not possible to run it out of > our data centers. Tracing showed that BPF program was the top > trigger of these direct map splits. It's often not easy to reproduce issues like these, but I've ran into that before for other Proof of Concept issues before and the solution has been a Linux selftest. For instance a "multithreaded" bombing for kmod can be triggered with lib/test_kmod.c and tools/testing/selftests/kmod/kmod.sh Would desinging a selftest to abuse eBPF JIT be a possible way to reproduce the issue? Luis