On Wed, Jul 17, 2013 at 01:17:44PM +0800, Sam Ben wrote: > On 07/12/2013 10:03 AM, Robin Holt wrote: > >We have been working on this since we returned from shutdown and have > >something to discuss now. We restricted ourselves to 2MiB initialization > >to keep the patch set a little smaller and more clear. > > > >First, I think I want to propose getting rid of the page flag. If I knew > >of a concrete way to determine that the page has not been initialized, > >this patch series would look different. If there is no definitive > >way to determine that the struct page has been initialized aside from > >checking the entire page struct is zero, then I think I would suggest > >we change the page flag to indicate the page has been initialized. > > > >The heart of the problem as I see it comes from expand(). We nearly > >always see a first reference to a struct page which is in the middle > >of the 2MiB region. Due to that access, the unlikely() check that was > >originally proposed really ends up referencing a different page entirely. > >We actually did not introduce an unlikely and refactor the patches to > >make that unlikely inside a static inline function. Also, given the > >strong warning at the head of expand(), we did not feel experienced > >enough to refactor it to make things always reference the 2MiB page > >first. > > > >With this patch, we did boot a 16TiB machine. Without the patches, > >the v3.10 kernel with the same configuration took 407 seconds for > >free_all_bootmem. With the patches and operating on 2MiB pages instead > >of 1GiB, it took 26 seconds so performance was improved. I have no feel > >for how the 1GiB chunk size will perform. > > How to test how much time spend on free_all_bootmem? We had put a pr_emerg at the beginning and end of free_all_bootmem and then used a modified version of script which record the time in uSecs at the beginning of each line of output. Robin > > > > >I am on vacation for the next three days so I am sorry in advance for > >my infrequent or non-existant responses. > > > > > >Signed-off-by: Robin Holt <holt@xxxxxxx> > >Signed-off-by: Nate Zimmer <nzimmer@xxxxxxx> > >To: "H. Peter Anvin" <hpa@xxxxxxxxx> > >To: Ingo Molnar <mingo@xxxxxxxxxx> > >Cc: Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx> > >Cc: Linux MM <linux-mm@xxxxxxxxx> > >Cc: Rob Landley <rob@xxxxxxxxxxx> > >Cc: Mike Travis <travis@xxxxxxx> > >Cc: Daniel J Blueman <daniel@xxxxxxxxxxxxxxxxxx> > >Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > >Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> > >Cc: Yinghai Lu <yinghai@xxxxxxxxxx> > >Cc: Mel Gorman <mgorman@xxxxxxx> > >-- > >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > >the body of a message to majordomo@xxxxxxxxxxxxxxx > >More majordomo info at http://vger.kernel.org/majordomo-info.html > >Please read the FAQ at http://www.tux.org/lkml/ -- 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>