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From: Baoquan He To: "Barry Song (Xiaomi)" Cc: akpm@linux-foundation.org, linux-mm@kvack.org, 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, youngjun.park@lge.com, jp.kobryn@linux.dev, usama.arif@linux.dev, shakeel.butt@linux.dev Subject: Re: [RFC PATCH 3/3] mm: entirely remove lru_add_drain in do_swap_page Message-ID: References: <20260611105124.98668-1-baohua@kernel.org> <20260611105124.98668-4-baohua@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260611105124.98668-4-baohua@kernel.org> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 1574A140005 X-Stat-Signature: 8tgeky4748refk8d9osztzq7opauuqx6 X-Rspam-User: X-HE-Tag: 1781228382-351477 X-HE-Meta: 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 rYUr+KdW sVRvxOmfb7O/Gtkz4sig9ub9aEcv0d1QJdU8N7oWvguJ0hJju4mNv7vOlTuIzG89txcdHyRjPYqca4vR9fbDS91o0833LCK5gLrkEJv2An4SDmylJxpvgPlNXqMc0bhYfi+QfqtNcKm+rSscogfgONn9EfouCUvdHQzuCkBrnBLaROex54mFxX+8g47EyxBw/TqKSIQXemtZzlEDFcNmu4l/tz3Czv0Qwbr7jSdcNfuIqY2Vb9SuUrnDUIcCuR3CPtYLsEvhyFMesXcawAq9B+ZOoWivhcp3UtMyda1ZFrw2XVrHPct/uWypXJuMbjDybFTpRkM7UaIMbD9FlLvH13PE547zRR/faN6T8V9H4FEumDr0= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 06/11/26 at 06:51pm, Barry Song (Xiaomi) wrote: > 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); Reviewed-by: Baoquan He > > /* > -- > 2.39.3 (Apple Git-146) >