On Fri, 21 Sep 2007 18:02:47 +0100 (BST) Hugh Dickins <[EMAIL PROTECTED]> wrote: > > 3. I want to *try* page->mapping overriding... store memory resource > > controller's > > information in page->mapping. By this, memory controller doesn't enlarge > > sizeof > > struct page. (works well in my small test.) > > Before doing that, I have to hide page->mapping from direct access. > > My own vote (nothing more) would be for you to set this aside until > some future time when there aren't a dozen developers all trampling > over each other in this area. > > They're invasive little changes affecting all filesystems, whereas what > we've done so far with page->mapping hasn't affected filesystems at all. > I found that each FS doesn't touch page->mapping so much as I expected. (except for ReiserFS) But ok, I admit changing this will confuse people.
> 3: well, saving memory is good, but I think it could wait until some > other time, particularly since the memory controller isn't in yet. > Yes, if extra field in page struct is not hazard to push memory controller, I don't have much motivation. Because extra 8 bytes makes page struct to be 64 bytes(in 64bit), extra 8 bytes is the last space, I think. > If we were to attack page->mapping to save memory from struct page, > then we should consider Magnus Damm's idea too: he suggested it could > be replaced by a pointer to the radixtree slot (something else needed > in the anon case), from which "index" could be deduced via alignment > instead of keeping it in struct page (details to be filled in ...) > There is a bit difference. My purpose is "avoid making struct page larger", not "making struct page smaller". > Or should I now leave PG_swapcache as is, > given your designs on page->mapping? > will conflict with my idea ? == http://marc.info/?l=linux-mm&m=118956492926821&w=2 == Anyway, I'm not in hurry about this patch-set. I'll see what memory controller will go. Other people seems to have an idea to implement pfn <-> container_info_per_page function. (But this kind of function is not welcomed always.) Thank you for comments. > p.s. Sorry to niggle, but next time, please say [PATCH 1/3] etc. > rather than [PATCH] Long Description [1/3], so it's easier to > sort the mail subjects by eye in limited columns - thanks. > sorry, I'll consider well next time. Thanks, -Kame - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
