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Thu, 02 Apr 2026 17:45:02 -0700 (PDT) Received: from localhost ([2603:7000:c00:3a00:365a:60ff:fe62:ff29]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8a596a0a655sm35304536d6.29.2026.04.02.17.45.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2026 17:45:02 -0700 (PDT) Date: Thu, 2 Apr 2026 20:45:01 -0400 From: Johannes Weiner To: "JP Kobryn (Meta)" Cc: linux-mm@kvack.org, willy@infradead.org, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, riel@surriel.com, kuba@kernel.org, edumazet@google.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v2] mm/vmpressure: skip socket pressure for costly order reclaim Message-ID: References: <20260402232511.17246-1-jp.kobryn@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260402232511.17246-1-jp.kobryn@linux.dev> X-Rspam-User: X-Stat-Signature: z3rr7rh36w31mdy5f677rdkzitfshnc5 X-Rspamd-Queue-Id: DF819A0006 X-Rspamd-Server: rspam09 X-HE-Tag: 1775177103-209412 X-HE-Meta: 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 TtpYDGxC YeLxQALzUfXZtwM+WGSSe78MFPtnpXrunjPD/jwflMlQn8DLeVC9nf7Ks7SZRWHvOxN/0 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: nOn Thu, Apr 02, 2026 at 04:25:11PM -0700, JP Kobryn (Meta) wrote: > When kswapd reclaims at high order due to fragmentation, vmpressure() can > report poor reclaim efficiency even though the system has plenty of free > memory. This is because kswapd scans many pages but finds little to reclaim > - the pages are actively in use and don't need to be freed. The resulting > scan:reclaim ratio triggers socket pressure, throttling TCP throughput > unnecessarily. > > Net allocations do not exceed order 3 (PAGE_ALLOC_COSTLY_ORDER), so high > order reclaim difficulty should not trigger socket pressure. The kernel > already treats this order as the boundary where reclaim is no longer > expected to succeed and compaction may take over. > > Make vmpressure() order-aware through an additional parameter sourced from > scan_control at existing call sites. Socket pressure is now only asserted > when order <= PAGE_ALLOC_COSTLY_ORDER. > > Memcg reclaim is unaffected since try_to_free_mem_cgroup_pages() always > uses order 0, which passes the filter unconditionally. Similarly, > vmpressure_prio() now passes order 0 internally when calling vmpressure(), > ensuring critical pressure from low reclaim priority is not suppressed by > the order filter. > > Signed-off-by: JP Kobryn (Meta) Acked-by: Johannes Weiner