From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: [PATCH/RFC 3/3] s390: query dynamic DEBUG_PAGEALLOC setting Date: Wed, 27 Jan 2016 14:09:09 +0100 Message-ID: <56A8C175.9030702@de.ibm.com> References: <1453799905-10941-1-git-send-email-borntraeger@de.ibm.com> <1453799905-10941-4-git-send-email-borntraeger@de.ibm.com> <20160126181903.GB4671@osiris> <20160127001918.GA7089@js1304-P5Q-DELUXE> <20160127005920.GB7089@js1304-P5Q-DELUXE> <56A8BB15.9070305@suse.cz> <56A8BC6D.9080101@de.ibm.com> <56A8C028.7050305@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <56A8C028.7050305@suse.cz> Sender: linux-arch-owner@vger.kernel.org List-Archive: List-Post: To: Vlastimil Babka , Joonsoo Kim , David Rientjes Cc: Heiko Carstens , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, x86@kernel.org List-ID: On 01/27/2016 02:03 PM, Vlastimil Babka wrote: > On 01/27/2016 01:47 PM, Christian Borntraeger wrote: >> On 01/27/2016 01:41 PM, Vlastimil Babka wrote: >>> On 01/27/2016 01:59 AM, Joonsoo Kim wrote: >>> >>> I think it might be worth also to convert debug_pagealloc_enabled() to be based >>> on static key, like I did for page_owner [1]. That should help make it possible >>> to have virtually no overhead when compiling kernel with CONFIG_DEBUG_PAGEALLOC >>> without enabling it boot-time. I assume it's one of the goals here? >> >> We could do something like that but dump_stack and setup of the initial identity >> mapping of the kernel as well as the initial page protection are not hot path >> as far as I can tell. Any other places? > > Well, mostly kernel_map_pages() which is used in page allocation hotpaths. Right. So indeed, static_key would be a good thing, but certainly an addon patch.