Messages in this thread | | | Date | Tue, 27 Sep 2005 23:08:21 +0200 | From | Pavel Machek <> | Subject | Re: [PATCH][Fix] Fix Bug #4959 (take 2) |
| |
Hi!
> > I do not really like new exports from swsusp.c, but I'm afraid > > there's no way around. > > Well, there is one, if we use a static buffer, as you propose, since > in that case we will not need get_usable_pages() etc. outside of > swsusp.c. The drawback of this, however, is that we will limit the > size of RAM for which it is possible to suspend (we need at least 1 page > for the PGD, 1 page for a PUD plus as many pages as there are GBs of > RAM for PMDs). If we want to cover the huge-RAM cases, the buffer will > be too large for the average case, but otherwise some boxes will not > be able to suspend.
1GB per 4K seems pretty much okay.
> > > The following patch fixes Bug #4959. For this purpose it creates temporary > > > page translation tables including the kernel mapping (reused) and the direct > > > mapping (created from scratch) and makes swsusp switch to these tables > > > right before the image is restored. > > > > Why do you need *two* mappings? Should not just kernel mapping be enough? > > The kernel mapping is for the kernel text. The direct mapping maps the physical > RAM linearly to the set of virtual addresses starting at > PAGE_OFFSET.
Could not you just add phys_to_virt at some strategic place?
> > Why? Reserve ten pages for them... static char resume_page_tables[10*PAGE_SIZE] does not > > sound that bad. > > That will allow us to suspend if there's no more that 8GB of RAM in the box. > Is it acceptable?
I'd say so.
> > > Moreover, such a code would have to be executed on every boot and the > > > temporary page tables would always be present in memory. > > > > Yep, but I do not see that as a big problem. > > OK > > I can reserve the static buffer (10 pages) in suspend.c and mark it as nosave. > The code that creates the mappings can stay in suspend.c either except it > won't need to call get_usable_page() and free_eaten_memory() any more > (__next_page() can be changed to get pages from the static buffer instead > of allocating them). The code can also be simplified a bit, as we assume that > there will be only one PGD entry in the direct mapping. > > If that sounds good to you, please confirm.
8GB limit seems good to me -- as long as it makes code significantly simpler. It would be nice if it was <20 lines. Pavel -- if you have sharp zaurus hardware you don't need... you know my address - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |