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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id d16sm861676qkl.7.2019.10.03.01.36.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Oct 2019 01:36:39 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v3 1/3] mm: kmemleak: Make the tool tolerant to struct scan_area allocation failures Date: Thu, 3 Oct 2019 04:36:39 -0400 Message-Id: <934700AE-CD78-43B8-A59B-2E968DA44DBB@lca.pw> References: <2ac37341-097e-17a2-fb6b-7912da9fa38e@ozlabs.ru> Cc: Catalin Marinas , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Michal Hocko , Matthew Wilcox In-Reply-To: <2ac37341-097e-17a2-fb6b-7912da9fa38e@ozlabs.ru> To: Alexey Kardashevskiy X-Mailer: iPhone Mail (17A844) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Oct 3, 2019, at 2:13 AM, Alexey Kardashevskiy wrote: >=20 > I came across this one while bisecting sudden drop in throughput of a 100G= bit Mellanox CX4 ethernet card in a PPC POWER9 > system, the speed dropped from 100Gbit to about 40Gbit. Bisect pointed at d= ba82d943177, this are the relevant config > options: >=20 > [fstn1-p1 kernel]$ grep KMEMLEAK ~/pbuild/kernel-le-4g/.config > CONFIG_HAVE_DEBUG_KMEMLEAK=3Dy > CONFIG_DEBUG_KMEMLEAK=3Dy > CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=3D16000 > # CONFIG_DEBUG_KMEMLEAK_TEST is not set > # CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF is not set > CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN=3Dy >=20 > Setting CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE=3D400 or even 4000 (this is wh= at KMEMLEAK_EARLY_LOG_SIZE is now in the master) > produces soft lockups on the recent upstream (sha1 a3c0e7b1fe1f): >=20 > [c000001fde64fb60] [c000000000c24ed4] _raw_write_unlock_irqrestore+0x54/0x= 70 > [c000001fde64fb90] [c0000000004117e4] find_and_remove_object+0xa4/0xd0 > [c000001fde64fbe0] [c000000000411c74] delete_object_full+0x24/0x50 > [c000001fde64fc00] [c000000000411d28] __kmemleak_do_cleanup+0x88/0xd0 > [c000001fde64fc40] [c00000000012a1a4] process_one_work+0x374/0x6a0 > [c000001fde64fd20] [c00000000012a548] worker_thread+0x78/0x5a0 > [c000001fde64fdb0] [c000000000135508] kthread+0x198/0x1a0 > [c000001fde64fe20] [c00000000000b980] ret_from_kernel_thread+0x5c/0x7c >=20 > KMEMLEAK_EARLY_LOG_SIZE=3D8000 works but slow. >=20 > Interestingly KMEMLEAK_EARLY_LOG_SIZE=3D400 on dba82d943177 still worked a= nd I saw my 100Gbit. Disabling KMEMLEAK also > fixes the speed (apparently). >=20 > Is that something expected? Thanks, It is expected that a debug option like this will make the system slower.=