On Wed, May 06, 2009 at 07:05:09AM +0800, Rafael J. Wysocki wrote: > On Tuesday 05 May 2009, Wu Fengguang wrote: > > On Mon, May 04, 2009 at 08:22:38AM +0800, Rafael J. Wysocki wrote: > > > From: Rafael J. Wysocki <rjw@xxxxxxx> > > > > > > Since the hibernation code is now going to use allocations of memory > > > to create enough room for the image, it can also use the page frames > > > allocated at this stage as image page frames. The low-level > > > hibernation code needs to be rearranged for this purpose, but it > > > allows us to avoid freeing a great number of pages and allocating > > > these same pages once again later, so it generally is worth doing. > > > > > > [rev. 2: Change the strategy of preallocating memory to allocate as > > > many pages as needed to get the right image size in one shot (the > > > excessive allocated pages are released afterwards).] > > > > Rafael, I tried out your patches and found doubled memory shrink speed! > > > > [ 579.641781] PM: Preallocating image memory ... done (allocated 383900 pages, 128000 image pages kept) > > [ 583.087875] PM: Allocated 1535600 kbytes in 3.43 seconds (447.69 MB/s) > > Unfortunately, I'm observing a regression and a huge one. > > On my Atom-based test box with 1 GB of RAM after a fresh boot and starting X > with KDE 4 there are ~256 MB free. To create an image we need to free ~300 MB > and that takes ~2 s with the old code and ~15 s with the new one. > > It helps to call shrink_all_memory() once with a sufficiently large argument > before the preallocation. [snip] > > At last, I'd express my major concern about the transition to preallocate > > based memory shrinking: will it lead to more random swapping IOs? > > Hmm. I don't see immediately why would it. Maybe the regression I'm seeing > is related to that ... So you do have swap file enabled? hibernate_preallocate_memory() will firstly try to allocate as much pages as possible(savable+free), and then to free up (allocated-image_size) pages. That means *all* swappable pages will be swapped out in the process - that's a major performance regression! And the zones are likely to be *over scanned* and go to *all unreclaimable* state! (Hopefully they may be already small at the time.) -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
