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Thu, 03 Sep 2026 07:32:41 -0700 (PDT) From: Bo Zhang X-Google-Original-From: Bo Zhang To: akpm@linux-foundation.org, vbabka@kernel.org, david@kernel.org Cc: surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, zhaonanzhe@xiaomi.com, lipengfei28@xiaomi.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 3/4] mm: compaction: don't skip proactive compaction for non-costly mTHP Date: Thu, 3 Sep 2026 22:32:21 +0800 Message-Id: <20260903143221.4108871-1-zhangbo56@xiaomi.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260825043833.2659350-4-zhangbo56@xiaomi.com> References: <20260825043833.2659350-4-zhangbo56@xiaomi.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: 17uq918pb3gobtmu9ri9e4w3qg8sbtc4 X-Rspamd-Queue-Id: 4D1C640015 X-HE-Tag: 1788445965-700258 X-HE-Meta: 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 F5xY6Jeo yosUs4aITErVo+qCxt7IdxYLslIzqsgrBcdac1nckDDKH7S7Z4LIF3WWtUoaI9EWG5eX1b6JGApZY1lBr3FG8UW7i3sSIr9gbli6a7pL+6adjO+Z6sS+hycK3qfyjT1tAJCqKE6P1WExTToV7UJ21pBKont+DGKyaXsBELdw/2AsAVeWDgOu+W3owWajM3V37eLvfXU8oL3UxEnFmxUCWQO4v2V58rS4QvKkzFNK1OjKkK3Bqph54H4eVYG7tGcGtVDUyA82STVZ34AqIcLxp/FkQVNYDRb/8xU/ORQnAmRiboYMVdfKFCyvTGMh1g/re6TcEq9kcn17P5mQ0iB0pcxKHY1nnaPzxgKZ0 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Thanks for the review. Sashiko says "Does this change miss an entry condition check in should_proactive_compact_node() in the same file? If kswapd is already active when kcompactd evaluates whether to start, should_proactive_compact_node() still unconditionally aborts ... Could this prevent proactive compaction from even starting for non-costly orders, defeating the updated mid-flight check entirely?" You're right. I only relaxed the mid-flight check in __compact_finished(), but should_proactive_compact_node() still bails out unconditionally when kswapd is running, so for non-costly mTHP orders proactive compaction never even starts and my change has no effect in the common case (kswapd running under memory pressure). In v2 I'll apply the same non-costly condition at the entry check: if (!sysctl_compaction_proactiveness) return false; if (costly && kswapd_is_running(pgdat)) return false; so the entry and mid-flight checks stay consistent. Bo