> 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? Yes, thanks for reminding, I am using 128 bit now, I will change it to 64 bit. Let me finish the v4 first. Thanks! Liang -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href