From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4846A41C69 for ; Wed, 19 Jun 2024 17:47:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718819281; cv=none; b=GHNrEzS4hKsXAveQpq7Iw1E+h9sZPcppfCQuBt6Ujl/VRymYo+G1jIuJ2t2zqITM7fQs2QXwdLwugzlrC506qCX7U+p+Ko72+nlXEvNmLMnjPbXAbDVTZuf4hdthMP6/OeNx197lm2Gz7i3gAW9gXRMJ1bgHwilHFZE5G6ACmJg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718819281; c=relaxed/simple; bh=jnQNEtVezKGMuCelVhsIXdC8qmM0neatMpvt3Q3wYPk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=h2Bg3ltPkuz2LhqX/PdTaBbyiZVo1vCKNNMiEXOG0rmFvTc0NSg0Ixv1SZzQnJUUWMunB7wZTJ7Oy5dZon2F1QXpoUTvbymnbSacMsnKDb11q9bLQvexbj9/H6RMruO5uEG//tUpmY02y2COHiZFu+1+KjJ37QLYvjwxr1OcSKI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=AXDSTMfk; arc=none smtp.client-ip=91.218.175.174 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="AXDSTMfk" X-Envelope-To: mhocko@suse.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1718819277; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=I36DV95vqg3WqUSWDkFF1xu/gEicJbY8yx8D+wSVUZc=; b=AXDSTMfkK8VrfSMgByU0uszIDqYXPWzUNL7x80mmYOZFY2TVPKas1ocvhN7g8qXV8qpwiR WPoRoZJysjCsATvhAoEYNCJglBpDR0cCYsaZj+i7iAsAvH5l/evuh0x0ACe/KjLkni78rN WUpmDuKMt8vlWNQNxh2ZTCkAOpkhw1I= X-Envelope-To: akpm@linux-foundation.org X-Envelope-To: torvalds@linux-foundation.org X-Envelope-To: kernel-team@meta.com X-Envelope-To: linux-mm@kvack.org X-Envelope-To: linux-kernel@vger.kernel.org X-Envelope-To: kyle@infradead.org Date: Wed, 19 Jun 2024 10:47:51 -0700 X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Shakeel Butt To: Michal Hocko Cc: Andrew Morton , Linus Torvalds , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kyle McMartin Subject: Re: [PATCH] mm: ratelimit oversized kvmalloc warnings instead of once Message-ID: <20240619174751.7r2s7iojxbaxpqlw@linux.dev> References: <20240618213421.282381-1-shakeel.butt@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT On Wed, Jun 19, 2024 at 10:48:07AM +0200, Michal Hocko wrote: > On Wed 19-06-24 10:30:46, Michal Hocko wrote: > > On Wed 19-06-24 01:03:16, Shakeel Butt wrote: > > > On Wed, Jun 19, 2024 at 09:19:41AM GMT, Michal Hocko wrote: > > > > On Tue 18-06-24 14:34:21, Shakeel Butt wrote: > > > > > At the moment oversize kvmalloc warnings are triggered once using > > > > > WARN_ON_ONCE() macro. One issue with this approach is that it only > > > > > detects the first abuser and then ignores the remaining abusers which > > > > > complicates detecting all such abusers in a timely manner. The situation > > > > > becomes worse when the repro has low probability and requires production > > > > > traffic and thus require large set of machines to find such abusers. In > > > > > Mera production, this warn once is slowing down the detection of these > > > > > abusers. Simply replace WARN_ON_ONCE with WARN_RATELIMIT. > > > > > > > > Long time ago, I've had a patch to do the once_per_callsite WARN. I > > > > cannot find reference at the moment but it used stack depot to note > > > > stacks that have already triggered. Back then there was no reponse on > > > > the ML. Should I try to dig deep and recover it from my archives? I > > > > think this is exactly kind of usecase where it would fit. > > > > > > > > > > Do you mean something like warn once per unique call stack? > > > > Exactly! > > > > > If yes then > > > I think that is better than the simple ratelimiting version as > > > ratelimiting one may still miss some abusers and also may keep warning > > > about the same abuser. Please do share your patch. > > > > https://lore.kernel.org/all/20170103134424.28123-1-mhocko@kernel.org/ > > Btw. the code has changed a lot since 2017 when this was posted so it > will likely need a lot of massaging to rebase. Also I am not entirely > sure it is ok to change WARN_ONCE semantic like that anymore. Maybe we > need an explicit variant that does this per-call-site warnings. It is a > notable difference between library functions which can be called from > different callpaths and those that are used from a single place. I do > not have much time to dig deeper into this but if you want to take over > then go ahead. I still think this is a useful WARN_ONCE or in general > do_something_once semantic. I think a separate variant like WARN_UNIQUE() would be better. I will look into this. Linus, please let me know if you have any concerns on the approach Michal is suggesting i.e. a variant for warn once for unique call stack. Shakeel