From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Gushchin Subject: Re: [PATCH 1/3] mm: introduce NR_INDIRECTLY_RECLAIMABLE_BYTES Date: Wed, 25 Apr 2018 18:23:04 +0100 Message-ID: <20180425172258.GA8052@castle> References: <08524819-14ef-81d0-fa90-d7af13c6b9d5@suse.cz> <20180411135624.GA24260@castle.DHCP.thefacebook.com> <46dbe2a5-e65f-8b72-f835-0210bc445e52@suse.cz> <20180412145702.GB30714@castle.DHCP.thefacebook.com> <69b4dcd8-1925-e0e8-d9b4-776f3405b769@codeaurora.org> <20180425125211.GB3410@castle> <20180425164845.GA7223@castle> <7fc2986e-b867-eb32-9124-d10ef6c1a3a3@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline In-Reply-To: <7fc2986e-b867-eb32-9124-d10ef6c1a3a3@suse.cz> Sender: linux-kernel-owner@vger.kernel.org To: Vlastimil Babka Cc: Vijayanand Jitta , vinayak menon , linux-mm@kvack.org, Andrew Morton , Alexander Viro , Michal Hocko , Johannes Weiner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Linux API List-Id: linux-api@vger.kernel.org On Wed, Apr 25, 2018 at 07:02:42PM +0200, Vlastimil Babka wrote: > On 04/25/2018 06:48 PM, Roman Gushchin wrote: > > On Wed, Apr 25, 2018 at 05:47:26PM +0200, Vlastimil Babka wrote: > >> On 04/25/2018 02:52 PM, Roman Gushchin wrote: > >>> On Wed, Apr 25, 2018 at 09:19:29AM +0530, Vijayanand Jitta wrote: > >>>>>>>> Idk, I don't like the idea of adding a counter outside of the vm counters > >>>>>>>> infrastructure, and I definitely wouldn't touch the exposed > >>>>>>>> nr_slab_reclaimable and nr_slab_unreclaimable fields. > >>>>>>> > >>>>>>> We would be just making the reported values more precise wrt reality. > >>>>>> > >>>>>> It depends on if we believe that only slab memory can be reclaimable > >>>>>> or not. If yes, this is true, otherwise not. > >>>>>> > >>>>>> My guess is that some drivers (e.g. networking) might have buffers, > >>>>>> which are reclaimable under mempressure, and are allocated using > >>>>>> the page allocator. But I have to look closer... > >>>>>> > >>>>> > >>>>> One such case I have encountered is that of the ION page pool. The page pool > >>>>> registers a shrinker. When not in any memory pressure page pool can go high > >>>>> and thus cause an mmap to fail when OVERCOMMIT_GUESS is set. I can send > >>>>> a patch to account ION page pool pages in NR_INDIRECTLY_RECLAIMABLE_BYTES. > >> > >> FYI, we have discussed this at LSF/MM and agreed to try the kmalloc > >> reclaimable caches idea. The existing counter could then remain for page > >> allocator users such as ION. It's a bit weird to have it in bytes and > >> not pages then, IMHO. What if we hid it from /proc/vmstat now so it > >> doesn't become ABI, and later convert it to page granularity and expose > >> it under a name such as "nr_other_reclaimable" ? > > > > I've nothing against hiding it from /proc/vmstat, as long as we keep > > the counter in place and the main issue resolved. > > Sure. > > > Maybe it's better to add nr_reclaimable = nr_slab_reclaimable + nr_other_reclaimable, > > which will have a simpler meaning that nr_other_reclaimable (what is other?). > > "other" can be changed, sure. nr_reclaimable is possible if we change > slab to adjust that counter as well - vmstat code doesn't support > arbitrary calculations when printing. Sure, but even just hiding a value isn't that easy now. So we have to touch the vmstat printing code anyway. Thanks!