linux-kernel - Re: [PATCHv2, RFC 12/30] thp, mm: add event counters for huge page alloc on write to a file

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Date:	Tue, 26 Mar 2013 10:40:12 +0200 (EET)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Dave Hansen <dave@...1.net>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hillf Danton <dhillf@...il.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2, RFC 12/30] thp, mm: add event counters for huge page
 alloc on write to a file

Dave Hansen wrote:
> On 03/14/2013 10:50 AM, Kirill A. Shutemov wrote:
> > --- a/include/linux/vm_event_item.h
> > +++ b/include/linux/vm_event_item.h
> > @@ -71,6 +71,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
> >  		THP_FAULT_FALLBACK,
> >  		THP_COLLAPSE_ALLOC,
> >  		THP_COLLAPSE_ALLOC_FAILED,
> > +		THP_WRITE_ALLOC,
> > +		THP_WRITE_FAILED,
> >  		THP_SPLIT,
> >  		THP_ZERO_PAGE_ALLOC,
> >  		THP_ZERO_PAGE_ALLOC_FAILED,
> 
> I think these names are a bit terse.  It's certainly not _writes_ that
> are failing and "THP_WRITE_FAILED" makes it sound that way.

Right. s/THP_WRITE_FAILED/THP_WRITE_ALLOC_FAILED/

> Also, why do we need to differentiate these from the existing anon-hugepage
> vm stats?  The alloc_pages() call seems to be doing the exact same thing in
> the end.  Is one more likely to succeed than the other?

Existing stats specify source of thp page: fault or collapse. When we
allocate a new huge page with write(2) it's nither fault nor collapse. I
think it's reasonable to introduce new type of event for that.

-- 
 Kirill A. Shutemov
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