Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 13 Apr 2023 08:55:15 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Jaewon Kim <jaewon31.kim@samsung.com>
Cc:     "T.J. Mercier" <tjmercier@google.com>,
        "jstultz@google.com" <jstultz@google.com>,
        "sumit.semwal@linaro.org" <sumit.semwal@linaro.org>,
        "daniel.vetter@ffwll.ch" <daniel.vetter@ffwll.ch>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "hannes@cmpxchg.org" <hannes@cmpxchg.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "jaewon31.kim@gmail.com" <jaewon31.kim@gmail.com>
Subject: Re: [PATCH v3] dma-buf/heaps: system_heap: avoid too much allocation
Message-ID: <ZDenU98chAfH9jSj@dhcp22.suse.cz>
References: <CABdmKX2fA2nXaSb8k+LE1yeso=ZnboDtxhzmjzrS35GSKv73hQ@mail.gmail.com>
 <ZDZ4j7UdBt32j28J@dhcp22.suse.cz>
 <ZDZqYTSHBNGLq0zI@dhcp22.suse.cz>
 <20230410073228.23043-1-jaewon31.kim@samsung.com>
 <20230412085726epcms1p7d2bec2526e47bd10a3b6ea6a113c9cc3@epcms1p7>
 <20230412094440epcms1p445319579ead0d0576bb616ebb07501b4@epcms1p4>
 <ZDaP4/PYyb9tKGQi@dhcp22.suse.cz>
 <20230412113759epcms1p8cb15b54e3a96c7616419cb030d16f804@epcms1p8>
 <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcms1p6>
 <20230413001658epcms1p611d149fcbbbd06fc17387724f4f16359@epcms1p6>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230413001658epcms1p611d149fcbbbd06fc17387724f4f16359@epcms1p6>
Precedence: bulk

On Thu 13-04-23 09:16:58, Jaewon Kim wrote:
> >On Wed, Apr 12, 2023 at 4:38?AM Jaewon Kim <jaewon31.kim@samsung.com> wrote:
> >
> >> Yes I think you're right. As a allocator, dma-buf system heap looks to be loose
> >> in memory allocation. Limiting dmabuf memory may be required. But I think there
> >> is no nice and reasonable way so far. And the dma-buf system heap is being
> >> widely used in Android mobile system. AFAIK the camera consumes huge memory
> >> through this dma-buf system heap. I actually even looked a huge size request
> >> over 2GB in one dma-buf request.
> >>
> >Hey can you point me to where you saw a request that big? That's a
> >non-buggy request?!
> 
> (let me resend as plain text)
> It was one of camera scenarios. I internally asked and heard that was not a bug
> but normal. I think 2GB looks too big for one graphics buffer but it could be
> for other purposes like camera. I think the system heap should support that.

Is that any of the upstream drivers or something sitting out of the
tree.

> Regarding __GFP_RETRY_MAYFAIL, we may need to say dma-buf system heap was
> designed to gather many pages up to a requested size. If mm returns NULL due to
> __GFP_RETRY_MAYFAIL, dma-buf system heap will release other already allocated
> pages, so that it may help to avoid oom.

This really depends on the other activity on the system. If you have a
more concurrent memory demand at the time then you might be just out of
the luck. Really, claiming huge portion of the memory shouldn't be done
nilly willy.
-- 
Michal Hocko
SUSE Labs