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McKenney" , Thomas Gleixner , "Theodore Y . Ts'o" , Joel Fernandes , Sebastian Andrzej Siewior , Oleksiy Avramchenko Subject: Re: [RFC-PATCH 2/4] mm: Add __rcu_alloc_page_lockless() func. Message-ID: <20201002090729.GU2628@hirez.programming.kicks-ass.net> References: <20200918194817.48921-1-urezki@gmail.com> <20200918194817.48921-3-urezki@gmail.com> <38f42ca1-ffcd-04a6-bf11-618deffa897a@suse.cz> <20200929220742.GB8768@pc636> <795d6aea-1846-6e08-ac1b-dbff82dd7133@suse.cz> <20201001192626.GA29606@pc636> <20201002071123.GB20872@dhcp22.suse.cz> <20201002085014.GC3227@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201002085014.GC3227@techsingularity.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 02, 2020 at 09:50:14AM +0100, Mel Gorman wrote: > On Fri, Oct 02, 2020 at 09:11:23AM +0200, Michal Hocko wrote: > > > +#define ___GFP_NO_LOCKS 0x800000u > > > > Even if a new gfp flag gains a sufficient traction and support I am > > _strongly_ opposed against consuming another flag for that. Bit space is > > limited. > > That is definitely true. I'm not happy with the GFP flag at all, the > comment is at best a damage limiting move. It still would be better for > a memory pool to be reserved and sized for critical allocations. This is one of the reasons I did a separate allocation function. No GFP flag to leak into general usage. > > Besides that we certainly do not want to allow craziness like > > __GFP_NO_LOCK | __GFP_RECLAIM (and similar), do we? > > That would deserve to be taken to a dumpster and set on fire. The flag > combination could be checked in the allocator but the allocator path fast > paths are bad enough already. Isn't that what we have CONFIG_DEBUG_VM for?