On 10/26/2016 03:06 AM, Li, Liang Z wrote: > I am working on Dave's new bitmap schema, I have finished the part of > getting the 'hybrid scheme bitmap' and found the complexity was more > than I expected. The main issue is more memory is required to save > the 'hybrid scheme bitmap' beside that used to save the raw page > bitmap, for the worst case, the memory required is 3 times than that > in the previous implementation. Really? Could you please describe the scenario where this occurs? > I am wondering if I should continue, as an alternative solution, how about using PFNs array when > inflating/deflating only a few pages? Things will be much more > simple. Yes, using pfn lists is more efficient than using bitmaps for sparse bitmaps. Yes, there will be cases where it is preferable to just use pfn lists vs. any kind of bitmap. But, what does it matter? At least with your current scheme where we go out and collect get_unused_pages(), we do the allocation up front. The space efficiency doesn't matter at all for small sizes since we do the constant-size allocation *anyway*. I'm also pretty sure you can pack the pfn and page order into a single 64-bit word and have no bitmap for a given record. That would make it pack just as well as the old pfns alone. Right? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
