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AFNElJ9QtPuyaZcAzmqTWZz+yRvOvOSzi2zr+rGzYwLcJkglEXW+1Z3bOuPzzmDLKKQWOFrIctDTd89gaJdelXk=@vger.kernel.org X-Gm-Message-State: AOJu0YzsMlhKVs1OrVPC13KfF13/7In0xGz+zQLlBSPz4ml+GYT6l1Jb KWZ2WDcaqM8l+gYx3u0g9fpE2s0nQThJvYgHcRdL4liE2lRdPAniKk9WjrwfQlnZQy+u1r47n6X N2IPBzWtHkoLZPS3lIJtP/jJ6CpOKkqY= X-Gm-Gg: AfdE7ckCQBc7/2iCOL19Wr7gDBpUorciw//mTn0yY2XsAsZs3vlMOUfxiszOUfETR7/ gowznEUj90vfQ2t9gOVRUzoFRkSGoX67Ga4AGoDXzfN0Uz0+FLO3Q4YlxfPcYmzQarPQ6fLr/PN 3rD44gdoDu2UUO8y1xtzn8t6wZKaKq8s/NOrR9vKtzeHPsIZwPhKtSkMuDOyiq1IFTsyPOKmG4C G8K0fJdOIpAA3Vb1292EkEM+SWfyOZDuApDW/1VblKMs+riMzoZPhsBJL8+B2e9HxCU7sxUWhnt 28/pbDH/WA5p0Rq/XeVl47qEOm1vYg== X-Received: by 2002:a17:907:c448:b0:bee:19d0:db92 with SMTP id a640c23a62f3a-c10803b52e5mr366822866b.49.1782296208510; Wed, 24 Jun 2026 03:16:48 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20260623231635.43086-1-baohua@kernel.org> <20260623231635.43086-4-baohua@kernel.org> In-Reply-To: <20260623231635.43086-4-baohua@kernel.org> From: Kairui Song Date: Wed, 24 Jun 2026 18:16:11 +0800 X-Gm-Features: AVVi8CcGjG7rTM6Nobr68lWdfX8Fp_VEvlB1uBNZ_hzUUIkKMFN6zCaJgc31nkU Message-ID: Subject: Re: [PATCH v2 3/4] mm: entirely remove lru_add_drain in do_swap_page To: "Barry Song (Xiaomi)" Cc: akpm@linux-foundation.org, linux-mm@kvack.org, baoquan.he@linux.dev, chrisl@kernel.org, david@kernel.org, jp.kobryn@linux.dev, liam@infradead.org, linux-kernel@vger.kernel.org, ljs@kernel.org, mhocko@suse.com, nphamcs@gmail.com, rppt@kernel.org, shakeel.butt@linux.dev, shikemeng@huaweicloud.com, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, youngjun.park@lge.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Jun 24, 2026 at 7:18=E2=80=AFAM 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 =3D mmap(0, SIZE, PROT_READ | PROT_WRITE, > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > > for (int i =3D 0; i < SIZE/sizeof(int); i++) > p[i] =3D i%64; > madvise((void *)p, SIZE, MADV_PAGEOUT); > for (int i =3D 0; i < SIZE/sizeof(int); i++) > p[i] =3D 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. > > Acked-by: Shakeel Butt > Reviewed-by: Baoquan He > 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 abd0adcf65f0..2983a6baf474 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 !=3D swapcache) > page =3D 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) > Thanks, I saw the previous discussed problem is address in the next patch, it's totally fine so: Reviewed-by: Kairui Song