On Tue, Nov 23, 2021 at 02:27:18PM -0800, Akilesh Kailash wrote: > On Tue, Nov 23, 2021 at 1:03 PM Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > Older devices do not get new kernel features, only LTS updates. On the > other hand, by having > it in user-space, we have more control by adding in new features. For > ex: On Android S, we > introduced the first version of Android COW format. Now in Android T, > we plan to support > new features by having XOR compression (which saves more space). While you are developing this, sure, you're finding new ways that make significant space savings and want to roll them out easily and the userspace approach helps you to do that. But the law of diminishing returns will eventually kick in, where you have reached a format that provides "good enough" space savings and then reducing the runtime performance penalty will become the overriding concern and that'll point back to an in-kernel solution. So that's the end point I think we are aiming for here. Combining the requirements to find a sweet spot between space saving and performance. By then, the ability still to make a tweak that saves a tiny bit more space isn't going to be worth paying an ongoing performance penalty for. (And there could still be some sort of ebpf-style option.) Alasdair -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
