Re: [PATCH v3 0/2] mm/swap: skip empty clusters in the swapoff scan
Andrew Morton <[email protected]>
| Newsgroups | gmane.linux.kernel,gmane.linux.kernel.mm |
|---|---|
| Message-ID | <[email protected]> |
On Fri, 7 Aug 2026 16:42:22 +0800 Baoquan He <[email protected]> wrote: > > I have no measured times yet, since that case has to be set up on purpose. > > What I did is the arithmetic for the case that skips best, > > For example 1T of swap with 256M slots with SWAPFILE_CLUSTER = 512 > > and everything free but the far end: > > > > - today: 256M table reads > > - with the skip: 512K counter reads > > > Maybe just use time to measure swapoff time consuming, just like below > as I did on a kvm guest, I guess a bare metal machine with larger system > ram could be more obvious? > > root@fedora:~# free -h > total used free shared buff/cache available > Mem: 3.8Gi 181Mi 3.6Gi 924Ki 72Mi 3.7Gi > Swap: 2.0Gi 18Mi 2.0Gi > root@fedora:~# time swapoff /dev/vdb > > real 0m0.101s > user 0m0.001s > sys 0m0.017s > root@fedora:~# swapon /dev/vdb > root@fedora:~# time swapoff /dev/vdb > > real 0m0.014s > user 0m0.003s > sys 0m0.001s > > Not sure if Andrew is asking for this. I think it's helpful to include such info. The audience for changelogs is more than swap developers! It's also an MM maintainer and -stable maintainers and other people who are all wondering "should I backport this for my users". Let's give them the means to determine that.