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Shutemov" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org Subject: Re: [RFC PATCH] mm, proc: report PR_SET_THP_DISABLE in proc In-Reply-To: <20181003073640.GF18290@dhcp22.suse.cz> Message-ID: References: <20180924195603.GJ18685@dhcp22.suse.cz> <20180924200258.GK18685@dhcp22.suse.cz> <0aa3eb55-82c0-eba3-b12c-2ba22e052a8e@suse.cz> <20180925202959.GY18685@dhcp22.suse.cz> <20180925150406.872aab9f4f945193e5915d69@linux-foundation.org> <20180926060624.GA18685@dhcp22.suse.cz> <20181002112851.GP18290@dhcp22.suse.cz> <20181003073640.GF18290@dhcp22.suse.cz> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 3 Oct 2018, Michal Hocko wrote: > > > So how about this? (not tested yet but it should be pretty > > > straightforward) > > > > Umm, prctl(PR_GET_THP_DISABLE)? > > /me confused. I thought you want to query for the flag on a > _different_ process. Why would we want to check three locations (system wide setting, prctl setting, madvise setting) to determine if a heap can be backed by thp? If the nh flag being exported to VmFlag is to be extended beyond what my patch did, I suggest (1) it does it for the system wide setting as well and/or (2) calling a helper function to determine if the vma could be backed by thp in the first place regardless of any setting to determine if nh/hg is important. The last thing I suggest is done is adding a third place to check.