linux-kernel - Re: [PATCHv4 18/39] thp, mm: add event counters for huge page alloc on write to a file

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Date:	Tue, 21 May 2013 13:54:45 -0700
From:	Dave Hansen <dave@...1.net>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
CC:	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: [PATCHv4 18/39] thp, mm: add event counters for huge page alloc
 on write to a file

On 05/11/2013 06:23 PM, Kirill A. Shutemov wrote:
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> index d4b7a18..584c71c 100644
> --- 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_ALLOC_FAILED,
>  		THP_SPLIT,
>  		THP_ZERO_PAGE_ALLOC,
>  		THP_ZERO_PAGE_ALLOC_FAILED,
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 7945285..df8dcda 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -821,6 +821,8 @@ const char * const vmstat_text[] = {
>  	"thp_fault_fallback",
>  	"thp_collapse_alloc",
>  	"thp_collapse_alloc_failed",
> +	"thp_write_alloc",
> +	"thp_write_alloc_failed",
>  	"thp_split",
>  	"thp_zero_page_alloc",
>  	"thp_zero_page_alloc_failed",

I guess these new counters are _consistent_ with all the others.  But,
why do we need a separate "_failed" for each one of these?  While I'm
nitpicking, does "thp_write_alloc" mean allocs or _successful_ allocs?
I had to look at the code to tell.

I thihk it's probably safe to combine this patch with the next one.
Breaking them apart just makes it harder to review.  If _anything_,
this, plus the use of the counters should go in to a different patch
from the true code changes in "mm: allocate huge pages in
grab_cache_page_write_begin()".
--
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