| Message ID | 1538727006-5727-2-git-send-email-arunks@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v5,1/2] memory_hotplug: Free pages as higher order | expand |
On Fri 05-10-18 13:40:06, Arun KS wrote: > They not only increase the code footprint, they actually make things > slower rather than faster. Remove them as contemporary hardware doesn't > need any hint. I agree with the change but it is much better to add some numbers whenever arguing about performance impact. > > Suggested-by: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Arun KS <arunks@codeaurora.org> > --- > mm/page_alloc.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7ab5274..90db431 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1258,14 +1258,10 @@ void __free_pages_core(struct page *page, unsigned int 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); > -- > 1.9.1 >
On 10/5/18 10:10 AM, Arun KS wrote: > They not only increase the code footprint, they actually make things > slower rather than faster. Remove them as contemporary hardware doesn't > need any hint. > > Suggested-by: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Arun KS <arunks@codeaurora.org> Yeah, a tight loop with fixed stride is a trivial case for hw prefetcher. Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > mm/page_alloc.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7ab5274..90db431 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1258,14 +1258,10 @@ void __free_pages_core(struct page *page, unsigned int 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); >
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 7ab5274..90db431 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1258,14 +1258,10 @@ void __free_pages_core(struct page *page, unsigned int 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);
They not only increase the code footprint, they actually make things slower rather than faster. Remove them as contemporary hardware doesn't need any hint. Suggested-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Arun KS <arunks@codeaurora.org> --- mm/page_alloc.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)