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Sun, 15 Feb 2026 15:21:01 -0800 (PST) MIME-Version: 1.0 References: <20260216-hibernate-perf-v3-0-74e025091145@tencent.com> <20260216-hibernate-perf-v3-2-74e025091145@tencent.com> In-Reply-To: <20260216-hibernate-perf-v3-2-74e025091145@tencent.com> From: Barry Song <21cnbao@gmail.com> Date: Mon, 16 Feb 2026 07:20:49 +0800 X-Gm-Features: AaiRm51jPFCewXyj-msKubNXn_1t8hUGFcByOC4NgVnj27CFj7IIHpXYi_25B1Q Message-ID: Subject: Re: [PATCH v3 2/3] mm, swap: reduce indention for hibernate allocation helper To: kasong@tencent.com Cc: linux-mm@kvack.org, Andrew Morton , Chris Li , Kemeng Shi , Nhat Pham , Baoquan He , Carsten Grohmann , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, "open list:SUSPEND TO RAM" , Carsten Grohmann Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: BA86B40003 X-Stat-Signature: zn3bfn5arc9pc8zmndd5qowsjfc6mbu8 X-Rspam-User: X-HE-Tag: 1771197662-119466 X-HE-Meta: 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 cAkxrISa d4K+kh3QV0MrZf6B0p96+TVF3mvSbzJjwxNOExc/3tngVsB4Whav/p1KD3w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Feb 16, 2026 at 3:00=E2=80=AFAM Kairui Song via B4 Relay wrote: > > From: Kairui Song > > It doesn't have to check the device flag, as the allocator will also > check the device flag and refuse to allocate if the device is not > writable. This might cause a trivial waste of CPU cycles of hibernate > allocation raced with swapoff, but that is very unlikely to happen. > Removing the check on the common path should be more helpful. > > Signed-off-by: Kairui Song > --- > mm/swapfile.c | 38 ++++++++++++++++++-------------------- > 1 file changed, 18 insertions(+), 20 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 32e0e7545ab8..0d1b17c99221 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1936,27 +1936,25 @@ swp_entry_t swap_alloc_hibernation_slot(int type) > > /* This is called for allocating swap entry, not cache */ > if (get_swap_device_info(si)) { I guess we could further reduce indentation by doing: if (!get_swap_device_info(si)) goto fail; > - if (si->flags & SWP_WRITEOK) { > - /* > - * Try the local cluster first if it matches the = device. If > - * not, try grab a new cluster and override local= cluster. > - */ > - local_lock(&percpu_swap_cluster.lock); > - pcp_si =3D this_cpu_read(percpu_swap_cluster.si[0= ]); > - pcp_offset =3D this_cpu_read(percpu_swap_cluster.= offset[0]); > - if (pcp_si =3D=3D si && pcp_offset) { > - ci =3D swap_cluster_lock(si, pcp_offset); > - if (cluster_is_usable(ci, 0)) > - offset =3D alloc_swap_scan_cluste= r(si, ci, NULL, pcp_offset); > - else > - swap_cluster_unlock(ci); > - } > - if (!offset) > - offset =3D cluster_alloc_swap_entry(si, N= ULL); > - local_unlock(&percpu_swap_cluster.lock); > - if (offset) > - entry =3D swp_entry(si->type, offset); > + /* > + * Try the local cluster first if it matches the device. = If > + * not, try grab a new cluster and override local cluster= . > + */ > + local_lock(&percpu_swap_cluster.lock); > + pcp_si =3D this_cpu_read(percpu_swap_cluster.si[0]); > + pcp_offset =3D this_cpu_read(percpu_swap_cluster.offset[0= ]); > + if (pcp_si =3D=3D si && pcp_offset) { > + ci =3D swap_cluster_lock(si, pcp_offset); > + if (cluster_is_usable(ci, 0)) > + offset =3D alloc_swap_scan_cluster(si, ci= , NULL, pcp_offset); > + else > + swap_cluster_unlock(ci); > } > + if (!offset) > + offset =3D cluster_alloc_swap_entry(si, NULL); > + local_unlock(&percpu_swap_cluster.lock); > + if (offset) > + entry =3D swp_entry(si->type, offset); > put_swap_device(si); > } > fail: > > -- > 2.52.0 > > Thanks Barry