From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f170.google.com (mail-ig0-f170.google.com [209.85.213.170]) by kanga.kvack.org (Postfix) with ESMTP id E10AE6B0035 for ; Thu, 31 Jul 2014 18:45:42 -0400 (EDT) Received: by mail-ig0-f170.google.com with SMTP id h3so2511767igd.3 for ; Thu, 31 Jul 2014 15:45:42 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id r18si17740807icg.26.2014.07.31.15.45.41 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 31 Jul 2014 15:45:42 -0700 (PDT) Date: Thu, 31 Jul 2014 15:45:40 -0700 From: Andrew Morton Subject: Re: [PATCH v2] mm: BUG when __kmap_atomic_idx equals KM_TYPE_NR Message-Id: <20140731154540.441ab79ff32ae5c10f64bcbd@linux-foundation.org> In-Reply-To: <53DA0C5A.3010409@codeaurora.org> References: <1406787871-2951-1-git-send-email-cpandya@codeaurora.org> <53DA0C5A.3010409@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Chintan Pandya Cc: David Rientjes , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Thu, 31 Jul 2014 14:58:58 +0530 Chintan Pandya wrote: > > > > I think Andrew's comment earlier was referring to the changelog only and > > not the patch, which looked correct. > > I think Andrew asked for a BUG case details also to justify the > overhead. But we have never encountered that BUG case. Present patch is > only logical fix to the code. However, in the fast path, if such > overhead is allowed, I can move BUG_ON out of any debug configs. > Otherwise, as per Andrew's suggestion, I will convert DEBUG_HIGHMEM into > DEBUG_VM which is used more frequently. The v1 patch added a small amount of overhead to kmap_atomic() for what is evidently a very small benefit. Yes, I suggest we remove CONFIG_DEBUG_HIGHMEM from the kernel entirely and switch all CONFIG_DEBUG_HIGHMEM sites to use CONFIG_DEBUG_VM. That way the BUG_ON which you believe is useful will be tested by more people more often. -- 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