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Tue, 19 Mar 2024 08:55:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id PscXOAlT+WV5CAAAD6G6ig (envelope-from ); Tue, 19 Mar 2024 08:55:37 +0000 Date: Tue, 19 Mar 2024 09:55:37 +0100 From: Michal Hocko To: liuhailong@oppo.com Cc: akpm@linux-foundation.org, nathan@kernel.org, ndesaulniers@google.com, trix@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, surenb@google.com, zhaoyang.huang@unisoc.com, quic_charante@quicinc.com, yuzhao@google.com Subject: Re: [PATCH v2] Revert "mm: skip CMA pages when they are not available" Message-ID: References: <20240314141516.31747-1-liuhailong@oppo.com> <20240315081803.2223-1-liuhailong@oppo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240315081803.2223-1-liuhailong@oppo.com> X-Rspam-User: X-Stat-Signature: ym319uct3z89ki6uifkb8tgqk6y9rkh4 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: F17D08000C X-HE-Tag: 1710838540-972802 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri 15-03-24 16:18:03, liuhailong@oppo.com wrote: > From: "Hailong.Liu" > > This reverts > commit b7108d66318a ("Multi-gen LRU: skip CMA pages when they are not eligible") > commit 5da226dbfce3 ("mm: skip CMA pages when they are not available") > > skip_cma may cause system not responding. if cma pages is large in lru_list > and system is in lowmemory, many tasks would direct reclaim and waste > cpu time to isolate_lru_pages and return. > > Test this patch on android-5.15 8G device > reproducer: > - cma_declare_contiguous 3G pages > - set /proc/sys/vm/swappiness 0 to enable direct_reclaim reclaim file > only. > - run a memleak process in userspace Does this represent a sane configuration? CMA memory is unusable for kernel allocations and memleak process is also hard to reclaim due to swap suppression. Isn't such a system doomed to struggle to reclaim any memory? Btw. how does the same setup behave with the regular LRU implementation? My guess would be that it would struggle as well. -- Michal Hocko SUSE Labs