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AJvYcCUa7HJPhPSUj/143H1nlVc1D82BDWfbEE+oV8X74/yPplAL0Nk9YwQwyRnGFwXgcqWYGpCn/wmIqg==@kvack.org X-Gm-Message-State: AOJu0Yx1eKqyAULn0WaAkpdIhA44lv8nFMSKZDiACFDuLuhC0UdaU/ht PvYEuQakaHu2YUgaOBdHy5ciIhomz4mHsK2jzOCyyGvygwkE58O69o2T1hlU1rJcILKV+9wnyKk 3rPS9c37LNzplNLICk8n7TJ82jZr86bcUrQ/Pl4g= X-Gm-Gg: ASbGnctsO9h2ZxO6zl/xgByxVvLkacVWHKTP27qFaI8Bpw760tcXET6veHgKHQMyAeV KsDGO0cqQK50WSVBJ+ZHPdHX+YL8Q9ni49q/UrxB375YKTDhzp74TO5uV79zYurtIbakzcNiZFU TIg79i3mObTA9ox3+k0OTHKW14c360SM1qjIZ80sy9tNy/5EDDyfIJxvkhlMbeZ9DYBSQzTb/CV ySD4iKxI6WbW4ethKxCoWL+MA== X-Google-Smtp-Source: AGHT+IFTeJN8C3xle4lIl1VszJExDN1ZHfVLP79fty/hDfsWXLVGkgQGQJiLdHdZfgQ2JCLp31hFHxNB8psS+idIW4o= X-Received: by 2002:a17:907:3d89:b0:b3e:f89e:9840 with SMTP id a640c23a62f3a-b50aa9a1e57mr2486576066b.20.1760423407136; Mon, 13 Oct 2025 23:30:07 -0700 (PDT) MIME-Version: 1.0 References: <20250929160727.a0119e93688378c570a3c550@linux-foundation.org> In-Reply-To: From: Kairui Song Date: Tue, 14 Oct 2025 14:29:30 +0800 X-Gm-Features: AS18NWClzCfLGHfCrmfpcSiXHHzGiCfKWn-Hrwy0D95p6tqbme-yce4l1LUUhnU Message-ID: Subject: Re: [Bug 220605] New: Very slow access on HDD when a swap partition is used on this HDD on kernel 6.16 To: Pierre Juhen Cc: Andrew Morton , bugzilla-daemon@kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E09D8C000A X-Stat-Signature: hwhq9d7w3oaf7enth1mtiw8t7gte9zp1 X-HE-Tag: 1760423408-873973 X-HE-Meta: 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 2Pzc6YsO 20fzRwafzoBrT2mRQuHVM6taVmPJ0JJpwdhHqzO0RzSERKcYszB042lH7DsNQVT2oI+au/Lid2ZtCJ4pWx65G3qXJUoj2SwJkWcACL1sHZRLJZ3CaGRqIQRrpVuCc17oSLnQNYZBeQOT9wBJR6MwAYxb8vMpgwTxFQIAssjN18kk8AvRDBSTbbDEnISG1moQbeP5CkaQ6HKGZyCGtWshNuRp6witP6PrcW28vbELwaIui9EtB3X9aCexr80TXWDfDNBXVHQ729J6fCDrsXUJb4Bhmht4LnF/VpXMjzQXG3IoKmM/kiAIwdd+DcmoE61uRaeVvQ4687UNE2V4dT+jXAPHB5p/bctZJRhhijQ42TNQ4l5fOlTTpnamDRSsaUbK7973KkjKXNOUtHnQRbiDENdJamg/5io28PAyEr1gkYcLstEhrbnPaiP4d03BLveMlo9AfQvEA+qhRtz9uzo7l6mz39g== 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 Sat, Oct 11, 2025 at 3:42=E2=80=AFAM Pierre Juhen wrote: > > Hi Andrew and people reading those lists, Hi Pierre, > > I still struggle to understand what is wrong with me. > > I rebuilt my mdadm + bcache array to be sure it was not something linked = to a (too) old configuration. Upgrading to 6.16.10 didn't change anything. > > One symptom of the problem I identified is the time of the swapoff comman= d (I have 32G, 12G are free and there is less than 1G in the swap) > > MiB Mem : 31952,0 total, 12646,2 free, 2226,8 used, 17587,5 buff/cac= he > MiB Swap: 36000,0 total, 35212,2 free, 787,8 used. 29725,2 avail Me= m > > > $ time sudo swapoff -a > > real 6m41,276s > user 0m0,005s > sys 0m0,028s > > Waiting for more than 6 minutes elapsed for 33 ms of work is bizarre. > > During that time, if I try to launch another tab with iotop, nothing is d= isplayed during at least one minute. > > During that time, my computer is almost idle. > > So it looks like swapoff and iotop are stucked, waiting for some kind of = a semaphore inside the kernel. > > Any idea to dig further ? > > Thanks, > > Pierre > > Le 30/09/2025 =C3=A0 01:07, Andrew Morton a =C3=A9crit : > > (switched to email. Please respond via emailed reply-to-all, not via the > bugzilla web interface). > > On Sat, 27 Sep 2025 08:07:59 +0000 bugzilla-daemon@kernel.org wrote: > > https://bugzilla.kernel.org/show_bug.cgi?id=3D220605 > > Bug ID: 220605 > Summary: Very slow access on HDD when a swap partition is used > on this HDD on kernel 6.16 > Product: Memory Management > Version: 2.5 > Hardware: Intel > OS: Linux > Status: NEW > Severity: high > Priority: P3 > Component: Page Allocator > Assignee: akpm@linux-foundation.org > Reporter: pierre.juhen@orange.fr > Regression: No > > Hello everybody, > > I have a strange behavior on my system (Fedora 42 up to date =3D> kernel = 6.16.8). > > You certainly do. I wonder what we did to cause this. > > I'll cc the MM development list. Please prefer to report issues over > email this way - we don't use bugzilla and it's rather annoying that MM > bugzilla even exists. > > > I have many disks but but my two swap partitions are on 2 HDD, sda and sd= b, > which are identical (SEAGATE Barracuda 2To). Swap partition on sda has a = higher > priority than the one on sdb. > > I don't use zram. > > When a swap partion is used, the disk on wich it seats is very slow. > > $ sudo hdparm -t /dev/sda > /dev/sda: > Timing buffered disk reads: 24 MB in 3.72 seconds =3D 6.46 MB/sec > > $ sudo hdparm -t /dev/sdb > /dev/sdb: > Timing buffered disk reads: 540 MB in 3.16 seconds =3D 170.85 MB/sec > pierre@pierre:~$ > > Sometimes, speed gets down to less than 2 MB/s. > > Lets turn swap off =3D> swapoff -a > > $ sudo hdparm -t /dev/sdb > /dev/sdb: > Timing buffered disk reads: 462 MB in 3.00 seconds =3D 153.75 MB/sec > > $ sudo hdparm -t /dev/sda > > /dev/sda: > Timing buffered disk reads: 474 MB in 3.00 seconds =3D 157.84 MB/sec > pierre@pierre:~$ > > Now speed is normal. > > Lets put swap on again =3D> sudo swapon -a > > Speed is still normal : > > $ sudo hdparm -t /dev/sda > /dev/sda: > Timing buffered disk reads: 612 MB in 3.01 seconds =3D 203.56 MB/sec > $ sudo hdparm -t /dev/sdb > /dev/sdb: > Timing buffered disk reads: 570 MB in 3.00 seconds =3D 189.95 MB/sec > pierre@pierre:~$ > > But swap is not used > > MiB Mem : 31952,0 total, 27091,7 free, 3057,6 used, 2343,0 buff/cac= he > MiB Swap: 36000,0 total, 36000,0 free, 0,0 used. 28894,4 avail Me= m > So the disk is already having a performance regression after swapon, while there is no memory pressure and SWAP is not used yet? Are you using swapon on the whole disk / partition or swapon on a file on top of the disk / partition? > > So I suspect that, when the swap is used, there is some sort of lock that= slows > the whole disk that contains the swap partition that is being used. > > Logically, the system becomes very slow. This is really strange if swap is not actually used. I just tested with HDD locally and didn't find anything wrong about it.