Re: [PATCH] mm: avoid tail page refcounting on non-THP compound pages

2015-03-25 Thread Hugh Dickins
On Thu, 26 Mar 2015, Kirill A. Shutemov wrote: > On Wed, Mar 25, 2015 at 03:48:48PM -0700, Hugh Dickins wrote: > > On Wed, 25 Mar 2015, Hugh Dickins wrote: > > > On Thu, 26 Mar 2015, Kirill A. Shutemov wrote: > > > > > > > > Since currently all THP pages are anonymous and all drivers pages are > >

Re: [PATCH] mm: avoid tail page refcounting on non-THP compound pages

2015-03-25 Thread Kirill A. Shutemov
On Wed, Mar 25, 2015 at 03:48:48PM -0700, Hugh Dickins wrote: > On Wed, 25 Mar 2015, Hugh Dickins wrote: > > On Thu, 26 Mar 2015, Kirill A. Shutemov wrote: > > > > > THP uses tail page refcounting to be able to split huge page at any > > > time. Tail page refcounting is not needed for rest users o

Re: [PATCH] mm: avoid tail page refcounting on non-THP compound pages

2015-03-25 Thread Hugh Dickins
On Wed, 25 Mar 2015, Hugh Dickins wrote: > On Thu, 26 Mar 2015, Kirill A. Shutemov wrote: > > > THP uses tail page refcounting to be able to split huge page at any > > time. Tail page refcounting is not needed for rest users of compound > > pages and it's harmful because of overhead. > > > > We t

Re: [PATCH] mm: avoid tail page refcounting on non-THP compound pages

2015-03-25 Thread Hugh Dickins
On Thu, 26 Mar 2015, Kirill A. Shutemov wrote: > THP uses tail page refcounting to be able to split huge page at any > time. Tail page refcounting is not needed for rest users of compound > pages and it's harmful because of overhead. > > We try to exclude non-THP pages from tail page refcounting

[PATCH] mm: avoid tail page refcounting on non-THP compound pages

2015-03-25 Thread Kirill A. Shutemov
THP uses tail page refcounting to be able to split huge page at any time. Tail page refcounting is not needed for rest users of compound pages and it's harmful because of overhead. We try to exclude non-THP pages from tail page refcounting using __compound_tail_refcounted() check. It excludes most