Re: [lc-devel] [linux-mm-cc] Re: Chunk list issues
Status: Beta
Brought to you by:
nitin_sf
From: <ac...@sa...> - 2006-07-01 20:12:08
|
Nitin Gupta wrote: > Hi Anderson, > >> >>> On 6/28/06, Anderson Briglia <bri...@gm...> wrote: >>> > > > I have a doubt related to chunk operations: >>> > > > >>> > > > - I guess you will use the virtual swap as the compressed >>> cache for >>> > > > anon pages, right? If yes, how will you swapin/swapout chunks? >>> If a >>> > > > single chunk points to a portion of a physical page, and the >>> > > > swapin/swapout operations handle entire pages of data. >>> > > >>> > > Yes, vswap is for anon pages. I think you are mistaken >>> somewhere...I'm not using >>> > > bio structs or anything to swapin/out pages from vswap. >>> > >>> > Ok. Will be possible to transfer pages from vswap to a 'real' swap >>> area? >>> > >>> >>> Yes, but 'procedure' will be same as for transferring a page from a >>> swap to any other swap: change it swp_entry_t to have 'type' for oth= er >>> swap and it will get written to this second swap. >> >> What will be the factor that determines when/which page will be >> migrated from vswap to real swap? >> > > vswap is full. Maybe others but I haven't thought of them yet :P > What should be considered here is how do we actually "migrate" a page like this? Because this isn't done very often normally (how often do you add/deactive swap areas) it is my understanding that this is an expensive process, which is why we can't really do it, a proposal is to instead of having a "vswap" area, that we allocate other physical swap areas in advance and do the interception of find_get_page & friends as is done in the git tree now. This way, when we need to kick out pages it is a very straightforward process, just put it in the pre-allocated swap slot. Of course this wastes swap space (probably disk) and doesn't work with no swap area at all, so maybe a mix where you can add vswap in some other way for no-swap area (where we never kick out pages anyways) purely as an swap entry id excercise. Greetings, Asbj=F8rn Sannes |