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# Re: [Xen-devel] [PATCH v4] memory_hotplug: Free pages as higher order

```On 2018-10-04 20:21, Michal Hocko wrote:
```
```On Wed 03-10-18 19:09:39, Arun KS wrote:
[...]
```
+static int online_pages_blocks(unsigned long start, unsigned long nr_pages)
```+{
+       unsigned long end = start + nr_pages;
+       int order, ret, onlined_pages = 0;
+
+       while (start < end) {
+               order = min(MAX_ORDER - 1UL, __ffs(start));
+
+               while (start + (1UL << order) > end)
+                       order--;
```
```
this really made me scratch my head. Wouldn't it be much simpler to do
the following?
order = min(MAX_ORDER - 1, get_order(end - start))?
```
```
Yes. Much better. Will change to,

order = min(MAX_ORDER - 1,
get_order(PFN_PHYS(end) - PFN_PHYS(start)));

```
```
```
```+
+               ret = (*online_page_callback)(pfn_to_page(start), order);
+               if (!ret)
+                       onlined_pages += (1UL << order);
+               else if (ret > 0)
+                       onlined_pages += ret;
+
+               start += (1UL << order);
+       }
+       return onlined_pages;
}
```
```[...]
```
-static void __init __free_pages_boot_core(struct page *page, unsigned int order)
```+void __free_pages_core(struct page *page, unsigned int order)
{
unsigned int nr_pages = 1 << order;
struct page *p = page;
unsigned int loop;

-       prefetchw(p);
-       for (loop = 0; loop < (nr_pages - 1); loop++, p++) {
-               prefetchw(p + 1);
+       for (loop = 0; loop < nr_pages; loop++, p++) {
__ClearPageReserved(p);
set_page_count(p, 0);
}
-       __ClearPageReserved(p);
-       set_page_count(p, 0);

page_zone(page)->managed_pages += nr_pages;
set_page_refcounted(page);
```
```
I think this is wort a separate patch as it is unrelated to the patch.
```
```Sure. Will split the patch.

Regards,
Arun

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