From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f172.google.com (mail-pd0-f172.google.com [209.85.192.172]) by kanga.kvack.org (Postfix) with ESMTP id 0F8E86B0035 for ; Tue, 19 Aug 2014 23:57:59 -0400 (EDT) Received: by mail-pd0-f172.google.com with SMTP id y13so11042403pdi.17 for ; Tue, 19 Aug 2014 20:57:59 -0700 (PDT) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTP id di1si29843104pdb.158.2014.08.19.20.57.52 for ; Tue, 19 Aug 2014 20:57:53 -0700 (PDT) Subject: [PATCH] [v2] TAINT_PERFORMANCE From: Dave Hansen Date: Tue, 19 Aug 2014 20:57:51 -0700 Message-Id: <20140820035751.08C980FB@viggo.jf.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: Dave Hansen , dave.hansen@linux.intel.com, peterz@infradead.org, mingo@redhat.com, ak@linux.intel.com, tim.c.chen@linux.intel.com, akpm@linux-foundation.org, cl@linux.com, penberg@kernel.org, linux-mm@kvack.org, kirill@shutemov.name, lauraa@codeaurora.org From: Dave Hansen Changes from v1: * remove schedstats * add DEBUG_PAGEALLOC and SLUB_DEBUG_ON -- I have more than once myself been the victim of an accidentally- enabled kernel config option being mistaken for a true performance problem. I'm sure I've also taken profiles or performance measurements and assumed they were real-world when really I was measuing the performance with an option that nobody turns on in production. A warning like this late in boot will help remind folks when these kinds of things are enabled. As for the patch... I originally wanted this for CONFIG_DEBUG_VM, but I think it also applies to things like lockdep and slab debugging. See the patch for the list of offending config options. I'm open to adding more, but this seemed like a good list to start. This could be done with Kconfig and an #ifdef to save us 8 bytes of text and the entry in the late_initcall() section. Doing it this way lets us keep the list of these things in one spot, and also gives us a convenient way to dump out the name of the offending option. The dump_stack() is really just to be loud. For anybody that *really* cares, I put the whole thing under #ifdef CONFIG_DEBUG_KERNEL. The messages look like this: [ 2.534574] CONFIG_LOCKDEP enabled [ 2.536392] Do not use this kernel for performance measurement. [ 2.547189] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.16.0-10473-gc8d6637-dirty #800 [ 2.558075] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 2.564483] 0000000080000000 ffff88009c70be78 ffffffff817ce318 0000000000000000 [ 2.582505] ffffffff81dca5b6 ffff88009c70be88 ffffffff81dca5e2 ffff88009c70bef8 [ 2.588589] ffffffff81000377 0000000000000000 0007000700000142 ffffffff81b78968 [ 2.592638] Call Trace: [ 2.593762] [] dump_stack+0x4e/0x68 [ 2.597742] [] ? oops_setup+0x2e/0x2e [ 2.601247] [] performance_taint+0x2c/0x3c [ 2.603498] [] do_one_initcall+0xe7/0x290 [ 2.606556] [] kernel_init_freeable+0x106/0x19a [ 2.609718] [] ? do_early_param+0x86/0x86 [ 2.613772] [] ? rest_init+0x150/0x150 [ 2.617333] [] kernel_init+0xe/0xf0 [ 2.620840] [] ret_from_fork+0x7c/0xb0 [ 2.624718] [] ? rest_init+0x150/0x150 Signed-off-by: Dave Hansen Cc: Peter Zijlstra Cc: Ingo Molnar Cc: ak@linux.intel.com Cc: tim.c.chen@linux.intel.com Cc: Andrew Morton Cc: Christoph Lameter Cc: Pekka Enberg Cc: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org Cc: kirill@shutemov.name Cc: lauraa@codeaurora.org --- b/include/linux/kernel.h | 1 + b/kernel/panic.c | 41 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+) diff -puN include/linux/kernel.h~taint-performance include/linux/kernel.h --- a/include/linux/kernel.h~taint-performance 2014-08-19 11:38:07.424005355 -0700 +++ b/include/linux/kernel.h 2014-08-19 11:38:20.960615904 -0700 @@ -471,6 +471,7 @@ extern enum system_states { #define TAINT_OOT_MODULE 12 #define TAINT_UNSIGNED_MODULE 13 #define TAINT_SOFTLOCKUP 14 +#define TAINT_PERFORMANCE 15 extern const char hex_asc[]; #define hex_asc_lo(x) hex_asc[((x) & 0x0f)] diff -puN kernel/panic.c~taint-performance kernel/panic.c --- a/kernel/panic.c~taint-performance 2014-08-19 11:38:28.928975233 -0700 +++ b/kernel/panic.c 2014-08-19 20:56:31.598705180 -0700 @@ -225,6 +225,7 @@ static const struct tnt tnts[] = { { TAINT_OOT_MODULE, 'O', ' ' }, { TAINT_UNSIGNED_MODULE, 'E', ' ' }, { TAINT_SOFTLOCKUP, 'L', ' ' }, + { TAINT_PERFORMANCE, 'Q', ' ' }, }; /** @@ -501,3 +502,43 @@ static int __init oops_setup(char *s) return 0; } early_param("oops", oops_setup); + +#ifdef CONFIG_DEBUG_KERNEL +#define TAINT_PERF_IF(x) do { \ + if (IS_ENABLED(CONFIG_##x)) { \ + do_taint = 1; \ + pr_warn("CONFIG_%s enabled\n", __stringify(x));\ + } \ + } while (0) + +static int __init performance_taint(void) +{ + int do_taint = 0; + + /* + * This should list any kernel options that can substantially + * affect performance. This is intended to give a big, fat + * warning during bootup so that folks have a fighting chance + * of noticing these things. + */ + TAINT_PERF_IF(LOCKDEP); + TAINT_PERF_IF(LOCK_STAT); + TAINT_PERF_IF(DEBUG_VM); + TAINT_PERF_IF(DEBUG_VM_VMACACHE); + TAINT_PERF_IF(DEBUG_VM_RB); + TAINT_PERF_IF(DEBUG_SLAB); + TAINT_PERF_IF(DEBUG_OBJECTS_FREE); + TAINT_PERF_IF(DEBUG_KMEMLEAK); + TAINT_PERF_IF(DEBUG_PAGEALLOC); + TAINT_PERF_IF(SLUB_DEBUG_ON); + + if (!do_taint) + return 0; + + pr_warn("Do not use this kernel for performance measurement."); + dump_stack(); + add_taint(TAINT_PERFORMANCE, LOCKDEP_STILL_OK); + return 0; +} +late_initcall(performance_taint); +#endif _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org