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Mon, 31 Oct 2022 20:18:44 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.7.0-alpha0-1087-g968661d8e1-fm-20221021.001-g968661d8 Mime-Version: 1.0 Message-Id: <9b71ae3e-7f53-4c9e-90c4-79d3d649f94c@app.fastmail.com> In-Reply-To: References: <20220913065423.520159-1-feng.tang@intel.com> <20220913065423.520159-2-feng.tang@intel.com> Date: Tue, 01 Nov 2022 00:18:19 +0000 From: "John Thomson" To: "Feng Tang" Cc: "Vlastimil Babka" , "Andrew Morton" , "Christoph Lameter" , "Pekka Enberg" , "David Rientjes" , "Joonsoo Kim" , "Roman Gushchin" , "Hyeonggon Yoo" <42.hyeyoo@gmail.com>, "Dmitry Vyukov" , "Jonathan Corbet" , "Andrey Konovalov" , "Hansen, Dave" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "kasan-dev@googlegroups.com" , "Robin Murphy" , "John Garry" , "Kefeng Wang" Subject: Re: [PATCH v6 1/4] mm/slub: enable debugging memory wasting of kmalloc Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 31 Oct 2022, at 11:42, Feng Tang wrote: > On Mon, Oct 31, 2022 at 10:05:58AM +0000, John Thomson wrote: >> On Mon, 31 Oct 2022, at 02:36, Feng Tang wrote: >> >> > >> >> > possibly relevant config options: >> >> > grep -E '(SLUB|SLAB)' .config >> >> > # SLAB allocator options >> >> > # CONFIG_SLAB is not set >> >> > CONFIG_SLUB=y >> >> > CONFIG_SLAB_MERGE_DEFAULT=y >> >> > # CONFIG_SLAB_FREELIST_RANDOM is not set >> >> > # CONFIG_SLAB_FREELIST_HARDENED is not set >> >> > # CONFIG_SLUB_STATS is not set >> >> > CONFIG_SLUB_CPU_PARTIAL=y >> >> > # end of SLAB allocator options >> >> > # CONFIG_SLUB_DEBUG is not set >> >> >> >> Also not having CONFIG_SLUB_DEBUG enabled means most of the code the >> >> patch/commit touches is not even active. >> >> Could this be some miscompile or code layout change exposing some >> >> different bug, hmm. >> >> Yes, it could be. >> >> >> Is it any different if you do enable CONFIG_SLUB_DEBUG ? >> >> No change >> >> >> Or change to CONFIG_SLAB? (that would be really weird if not) >> >> This boots fine >> >> > I haven't found any clue from the code either, and I compiled >> > kernel with the config above and tested booting on an Alder-lake >> > desktop and a QEMU, which boot fine. >> > >> > Could you provide the full kernel config and demsg (in compressed >> > format if you think it's too big), so we can check more? >> >> Attached >> >> > Thanks, >> > Feng >> >> vmlinux is bigger, and entry point is larger (0x8074081c vs 0x807407dc revert vs 0x8073fcbc), >> so that may be it? Or not? >> revert + SLUB_DEBUG + SLUB_DEBUG_ON is bigger still, but does successfully boot. >> vmlinux entry point is 0x8074705c > > Thanks for prompt info! > > As I can't reproduce it locally yet, could you help try 3 tests separately: > * change the O2/O3 compile option to O1 > * try the attached 0001 patch (which cut part of commit) > * try attached 0001+0002 patch None of these changed my outcome. I also tried compiling the same linux tree & config with the Bootlin toolchain (mipsel-buildroot-linux-gnu-gcc.br_real (Buildroot 2021.11-4428-g6b6741b) 12.2.0) with the same results. I will look into finding or building a mips clang toolchain. No JTAG capability to debug, sorry. I get the same outcome with either the ZBOOT vmlinuz, or vmlinux Same happening with 6.1-rc3 After some blind poking around changing (how much of the commit affected) mm/slub.c, I may have got lucky. it appears as though this is all I need to boot: (against 6.1-rc3), and with the Bootlin toolchain. Will test my other build system as well. --- a/mm/slub.c +++ b/mm/slub.c @@ -3276,7 +3276,7 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, c = slub_get_cpu_ptr(s->cpu_slab); #endif - p = ___slab_alloc(s, gfpflags, node, addr, c, orig_size); + p = ___slab_alloc(s, gfpflags, node, addr, c, 0); #ifdef CONFIG_PREEMPT_COUNT slub_put_cpu_ptr(s->cpu_slab); #endif Would like to hear your thoughts, but I will keep digging. > > Thanks! > > > - Feng > > > > > Attachments: > * 0001-reduced-slub-patch.patch > * 0002-reorder-the-partial_context-initialization.patch -- John Thomson