From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pekka Enberg Subject: Re: [Bug #13319] Page allocation failures with b43 and p54usb Date: Tue, 30 Jun 2009 11:24:53 +0300 Message-ID: <84144f020906300124n24e206b5tc85dd5cc4661bde7@mail.gmail.com> References: <5Hhc7UkUKEO.A.fNH.4kASKB@chimera> <4A48F114.1010702@lwfinger.net> <84144f020906292355o7cf63f7ch47bd19961cf92da3@mail.gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:date:x-google-sender-auth:message-id:subject:from:to:cc :content-type:content-transfer-encoding; bh=sXgZgASwQJKFGoMeaypuQo0r7FknRa5UWzVAP1/KC6A=; b=TiCyVrgKag7CtVnBu9yp53ZvP9JGpTAojXhUR+3fUTCVK8HMqy4JhlDwmRfdMAxpYK 4hJh6Bh7u4Zlze3hsP2pyEd8q1O+CBdPSGEJdyQYY+22M7dP8LMoDx7Pyiy7KtSjfuSy XDgGjsWMovg0JPxfHfg/mBnsTud5E+5BqQsxY= In-Reply-To: Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="iso-8859-1" To: David Rientjes Cc: Larry Finger , "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Johannes Berg , Christoph Lameter Hi David, On Tue, 30 Jun 2009, Pekka Enberg wrote: >> > I'd disagree with disabling slub debugging by default for caches w= here >> > oo_order(s->min) increases as the result of using it. =A0This part= icular >> > page allocation failure is happening for, presumably, kmalloc-4096= , and >> > the system has 4K pages. =A0Disabling debugging for that cache (an= d any of >> > its aliases) implicitly will lead to errors going undiagnosed as a= result. >> >> Well, I obviously don't agree here because kmalloc-4096 debugging >> causes problems in the real world. On Tue, Jun 30, 2009 at 10:47 AM, David Rientjes w= rote: > I don't think CONFIG_SLUB_DEBUG_ON is generally the configuration use= d in > the real world. It is, hence the epic bug report that's eaten too many man hours already! Look, we encourage _testers_ to turn all as much as debugging options as possible so we catch bugs early. That why the only sane defaults are the ones that don't cause other problems! I don't know why you want to argue this. It's simply not an option to say "stupid user, fix your config" in core code like the slab allocator. Enabling CONFIG_SLUB_DEBUG_ON is a very reasonable thing to do when you are a tester looking for bugs. On Tue, 30 Jun 2009, Pekka Enberg wrote: >> So we should fix SLUB debugging as outlined by Mel Gorman and >> Christoph Lameter. I simply haven't had the time to do it. Patches a= re >> welcome! On Tue, Jun 30, 2009 at 10:47 AM, David Rientjes w= rote: > You're referring to `slub_debug=3DA'? =A0I think CONFIG_SLUB_DEBUG_ON= should > continue to enable debugging on all slab caches and in instances wher= e it > causes page allocation failures such in Larry's case because > oo_order(s->min) with debugging on is greater than oo_order(s->min) w= ith > debugging off, you can emit a friendly warning in your recently added > slab_out_of_memory() about using `slab_debug=3D-,'. > > We have a disagreement about which is the default behavior, but I wou= ld > opt on the side of adding exemptions to a debug configuration option = as > opposed to requiring additional command line parameters to be fully > enabled. Yup, I was referring to slub_debug=3DA and no, I don't agree with you that it should be on by default. Only people who know what they're doing should enable the option and a random tester by definition doesn't (no offence to Mr. Random Tester). Pekka