Messages in this thread | | | Date | Wed, 17 Jul 2013 13:17:44 +0800 | From | Sam Ben <> | Subject | Re: [RFC 0/4] Transparent on-demand struct page initialization embedded in the buddy allocator |
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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?
> > 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@sgi.com> > Signed-off-by: Nate Zimmer <nzimmer@sgi.com> > To: "H. Peter Anvin" <hpa@zytor.com> > To: Ingo Molnar <mingo@kernel.org> > Cc: Linux Kernel <linux-kernel@vger.kernel.org> > Cc: Linux MM <linux-mm@kvack.org> > Cc: Rob Landley <rob@landley.net> > Cc: Mike Travis <travis@sgi.com> > Cc: Daniel J Blueman <daniel@numascale-asia.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Greg KH <gregkh@linuxfoundation.org> > Cc: Yinghai Lu <yinghai@kernel.org> > Cc: Mel Gorman <mgorman@suse.de> > -- > 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/
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