Messages in this thread | | | Subject | Re: Regression - locking (all from 2.6.28) | From | Catalin Marinas <> | Date | Fri, 06 Mar 2009 17:18:08 +0000 |
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On Fri, 2009-03-06 at 08:52 -0800, Dave Hansen wrote: > On Fri, 2009-03-06 at 16:40 +0000, Catalin Marinas wrote: > > It seems that node_start_pfn() isn't present on all the architectures. I > > ended up with something like below: > > > > + /* struct page scanning for each node */ > > + for_each_online_node(i) { > > + pg_data_t *pgdat = NODE_DATA(i); > > + unsigned long start_pfn = pgdat->node_start_pfn; > > + unsigned long end_pfn = start_pfn + > > + pgdat->node_spanned_pages - 1; > > + unsigned long pfn; > > + > > + for (pfn = start_pfn; pfn < end_pfn; pfn++) { > > + struct page *page; > > + > > + if (!pfn_valid(pfn)) > > + continue; > > + page = pfn_to_page(pfn); > > + /* only scan if page is in use */ > > + if (page_count(page) == 0) > > + continue; > > + scan_block(page, page + 1, NULL); > > + } > > + } > > What does scan_block() actually scan? Is that second argument > inclusive?
No, it's exclusive. In the above case, it just scans a struct page at the given pointer.
> I think you will miss scanning the contents of the last 'struct page' if > you do it this way because of the -1 you do to end_pfn.
Fixed.
> > Are the pgdat->node_start_pfn and pgdat->node_spanned_pages always > > valid? Thanks. > > The variables themselves? I'm sure there's a window in early boot where > they aren't valid, but other than that they should be OK unless you're > int the middle of a hotplug operation. > > See pgdat_resize_(un)lock() in include/linux/memory_hotplug.h.
I wouldn't hold a lock for that long. It's not really critical to scan all the page structures at a time as there are subsequent scans as well, so some can be missed.
-- Catalin
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