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Fri, 10 Apr 2026 03:14:00 -0700 (PDT) Date: Fri, 10 Apr 2026 11:13:59 +0100 From: Matt Fleming To: Matt Fleming Cc: Andrew Morton , Christoph Hellwig , Jens Axboe , Sergey Senozhatsky , Roman Gushchin , Minchan Kim , kernel-team@cloudflare.com, Johannes Weiner , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Zi Yan , Axel Rasmussen , Yuanchu Xie , Wei Xu , David Hildenbrand , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: Require LRU reclaim progress before retrying direct reclaim Message-ID: References: <20260303115358.1323188-1-matt@readmodwrite.com> <20260410094157.2895775-1-matt@readmodwrite.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260410094157.2895775-1-matt@readmodwrite.com> On Fri, Apr 10, 2026 at 10:41:56AM +0100, Matt Fleming wrote: > From: Matt Fleming > > should_reclaim_retry() uses zone_reclaimable_pages() to estimate whether > retrying reclaim could eventually satisfy an allocation. It's possible > for reclaim to make minimal or no progress on an LRU type despite having > ample reclaimable pages, e.g. anonymous pages when the only swap is > RAM-backed (zram). This can cause the reclaim path to loop indefinitely. > > Track LRU reclaim progress (anon vs file) through a new struct > reclaim_progress passed out of try_to_free_pages(), and only count a > type's reclaimable pages if at least reclaim_progress_pct% was actually > reclaimed in the last cycle. > > The threshold is exposed as /proc/sys/vm/reclaim_progress_pct (default > 1, range 0-100). Setting 0 disables the gate and restores the previous > behaviour. Environments with only RAM-backed swap (zram) and small > memory may need a higher value to prevent futile anon LRU churn from > keeping the allocator spinning. > > Suggested-by: Johannes Weiner > Signed-off-by: Matt Fleming > --- > include/linux/swap.h | 13 +++++- > mm/page_alloc.c | 101 +++++++++++++++++++++++++++++++++++-------- > mm/vmscan.c | 72 ++++++++++++++++++++++-------- > 3 files changed, 146 insertions(+), 40 deletions(-) Whoops, I fat-fingered this and sent it as a reply. I'll send it again as a separate patch. My bad.