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:	Fri, 05 Apr 2013 12:05:45 +0800
From:	Ric Mason <ric.masonn@...il.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
CC:	Dave Hansen <dave@...1.net>,
	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

Hi Kirill,
On 03/26/2013 04:40 PM, Kirill A. Shutemov wrote:
> 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.

Why when we allocated a new huge page with write(2) is not a write fault?

>

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