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b=olqx5g2thmz3pld3Q7jFbx2ndbz9i6fwyVTfR+AQ6Rzb1j50Mgv48OaXuQ1K3EV3v 5Q3t20cNEy9SFZKKy0VAIxfEh5LYaTpcSjqrpPHvyh9tDUZ8cRfmHDeMw6H8msogmk 7oob3s1OHFpEIhO5kXu+tvEs0mPC0hYnDECqTTFUNeLR6h/pmm7heAhOc732X5CjMf 8q8AH8i9DUXWjZq+W/mjFNTyTkeWnw5CBE1xSFSeg7DktaD6q2F8yVdR7edeZALK/K j8GGn8HUWWvpcvOD+PEAnpInd0nFSgpQXwS48cO+IiawrtSk6/yMpDuRC1qGMih4ZU wXv13/+Gcj5Zw== From: "Barry Song (Xiaomi)" To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, baoquan.he@linux.dev, youngjun.park@lge.com, jp.kobryn@linux.dev, usama.arif@linux.dev, shakeel.butt@linux.dev, "Barry Song (Xiaomi)" Subject: [RFC PATCH 3/3] mm: entirely remove lru_add_drain in do_swap_page Date: Thu, 11 Jun 2026 18:51:24 +0800 Message-Id: <20260611105124.98668-4-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20260611105124.98668-1-baohua@kernel.org> References: <20260611105124.98668-1-baohua@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 34281140007 X-Rspam-User: X-Stat-Signature: yrtby67wbuid71wq9wtjr4zbkbj7mf7t X-Rspamd-Server: rspam09 X-HE-Tag: 1781175107-317893 X-HE-Meta: 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 gt9JbRjm NSC5SvkSVbDguC5boLmyhfFalvRJgvJGI2cCL0rr51WDyVFkP1iXGTMjMMEMSsvV37RqChtE8iURjCPL1jTh5HNsPwz+6KValZw47EljCUFzRzHE4vZ4EYEDDOLza9jaHe/7gmiie1+bErMpjZyuzkWYVXBb0EFR/qGuJOsc5sdI2Wf4gys2LwqelEdFNQBKprh7rrmO36hrXKNyz8wkt1I+j/ybd99EqjvugoE09ENMXHbyxVRV6qWPWUb2Vrds5UnyGcPEkwfEacJ2X0hPapgOOfw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: We are doing a lot of redundant lru_add_drain() calls in do_swap_page(), especially for synchronous I/O devices. For example, the test program below currently ends up draining lru_cache 100% of the time: int main(int argc, char *argv[]) { int i; #define SIZE 100*1024*1024 while(1) { volatile int *p = mmap(0, SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); for (int i = 0; i < SIZE/sizeof(int); i++) p[i] = i%64; madvise((void *)p, SIZE, MADV_PAGEOUT); for (int i = 0; i < SIZE/sizeof(int); i++) p[i] = i%64; munmap(p, SIZE); } return 0; } Folio reuse now relies primarily on the exclusive hint, making lru_cache draining to drop the refcount in lru_cache largely irrelevant. Signed-off-by: Barry Song (Xiaomi) --- mm/memory.c | 10 ---------- 1 file changed, 10 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index ce8ef27e7a54..b5a78670bcc8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4903,16 +4903,6 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) } else if (folio != swapcache) page = folio_page(folio, 0); - /* - * If we want to map a page that's in the swapcache writable, we - * have to detect via the refcount if we're really the exclusive - * owner. Try removing the extra reference from the local LRU - * caches if required. - */ - if ((vmf->flags & FAULT_FLAG_WRITE) && - !folio_test_ksm(folio) && !folio_test_lru(folio)) - lru_add_drain(); - folio_throttle_swaprate(folio, GFP_KERNEL); /* -- 2.39.3 (Apple Git-146)