I'd like F11 to be more useful for disk power management. This involves tuning various parameters in order to reduce disk access. There are some tradeoffs involved, so I'd like feedback before pushing much of this. The first is relatime. I've just pushed Ingo's smarter relatime code towards upstream again. In this configuration atime will only be updated if the current atime is either older than ctime or mtime, or if the current atime is more than a day in the past. The amount of time required before atime is updated will be a tunable, and a norelatime mount parameter will be available to mount filesystems without this behaviour. This shouldn't affect the behaviour of any applications. The second is to increase the value of dirty_writeback_centisecs. This will result in dirty data spending more time in memory before being pushed out to disk. This is probably more controversial. The effect of this is that a power interruption will potentially result in more data being lost. It doesn't alter the behaviour of fsync(), so paranoid applications will still get to ensure that their data is on disk. Of course, it would also be helpful to stop applications generating dirty pages where possible. This would obviously be reverted if the system enters a critical power state. Thirdly, I'd like to enable laptop mode by default. The effect of this is that any access that goes to disk will trigger an opportunistic flushing of dirty data shortly afterwards. To an extent this mitigates the change to dirty_writeback_centisecs, but there's obviously still some increased chance of data loss. The combination of these features should result in (on average) fewer disk accesses and so (on average) should provide better performance. There's a chance that some usage patterns will fall foul of this and lose performance, so if we do this I'd like to do it sufficiently early in the cycle that we can get real-world feedback. Any thoughts? -- Matthew Garrett | mjg59@xxxxxxxxxxxxx -- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
