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From: Mel Gorman <mgorman@techsingularity.net>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Linux-MM <linux-mm@kvack.org>,
	Linux-FSDevel <linux-fsdevel@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>, Jan Kara <jack@suse.cz>,
	Andi Kleen <ak@linux.intel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Dave Chinner <david@fromorbit.com>
Subject: Re: [PATCH 1/8] mm, page_alloc: Enable/disable IRQs once when freeing a list of pages
Date: Wed, 18 Oct 2017 11:15:47 +0100
Message-ID: <20171018101547.mjycw7zreb66jzpa@techsingularity.net> (raw)
In-Reply-To: <bcd95a87-3f63-9f5d-77a0-2b2115f53919@suse.cz>

On Wed, Oct 18, 2017 at 11:02:18AM +0200, Vlastimil Babka wrote:
> On 10/18/2017 09:59 AM, Mel Gorman wrote:
> > Freeing a list of pages current enables/disables IRQs for each page freed.
> > This patch splits freeing a list of pages into two operations -- preparing
> > the pages for freeing and the actual freeing. This is a tradeoff - we're
> > taking two passes of the list to free in exchange for avoiding multiple
> > enable/disable of IRQs.
> 
> There's also some overhead of storing pfn in page->private, but all that
> seems negligible compared to irq disable/enable...
> 

Exactly and it's cheaper than doing a second page to pfn lookup.

> <SNIP>
> Looks good.
> 
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> 
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
> 

Thanks.

> A nit below.
> 
> > @@ -2647,11 +2663,25 @@ void free_hot_cold_page(struct page *page, bool cold)
> >  void free_hot_cold_page_list(struct list_head *list, bool cold)
> >  {
> >  	struct page *page, *next;
> > +	unsigned long flags, pfn;
> > +
> > +	/* Prepare pages for freeing */
> > +	list_for_each_entry_safe(page, next, list, lru) {
> > +		pfn = page_to_pfn(page);
> > +		if (!free_hot_cold_page_prepare(page, pfn))
> > +			list_del(&page->lru);
> > +		page->private = pfn;
> 
> We have (set_)page_private() helpers so better to use them (makes it a
> bit easier to check for all places where page->private is used to e.g.
> avoid a clash)?
> 

Agreed and it's trivial to do so

---8<---
mm, page_alloc: Enable/disable IRQs once when freeing a list of page -fix

Use page_private and set_page_private helpers.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
 mm/page_alloc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 167e163cf733..092973014c1e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2670,14 +2670,14 @@ void free_hot_cold_page_list(struct list_head *list, bool cold)
 		pfn = page_to_pfn(page);
 		if (!free_hot_cold_page_prepare(page, pfn))
 			list_del(&page->lru);
-		page->private = pfn;
+		set_page_private(page, pfn);
 	}
 
 	local_irq_save(flags);
 	list_for_each_entry_safe(page, next, list, lru) {
-		unsigned long pfn = page->private;
+		unsigned long pfn = page_private(page);
 
-		page->private = 0;
+		set_page_private(page, 0);
 		trace_mm_page_free_batched(page, cold);
 		free_hot_cold_page_commit(page, pfn, cold);
 	}

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  reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-18  7:59 [PATCH 0/8] Follow-up for speed up page cache truncation v2 Mel Gorman
2017-10-18  7:59 ` [PATCH 1/8] mm, page_alloc: Enable/disable IRQs once when freeing a list of pages Mel Gorman
2017-10-18  9:02   ` Vlastimil Babka
2017-10-18 10:15     ` Mel Gorman [this message]
2017-10-18  7:59 ` [PATCH 2/8] mm, truncate: Do not check mapping for every page being truncated Mel Gorman
2017-10-19  8:11   ` Jan Kara
2017-10-18  7:59 ` [PATCH 3/8] mm, truncate: Remove all exceptional entries from pagevec under one lock Mel Gorman
2017-10-18  7:59 ` [PATCH 4/8] mm: Only drain per-cpu pagevecs once per pagevec usage Mel Gorman
2017-10-19  9:12   ` Vlastimil Babka
2017-10-19  9:33     ` Mel Gorman
2017-10-19 13:21       ` Vlastimil Babka
2017-10-18  7:59 ` [PATCH 5/8] mm, pagevec: Remove cold parameter for pagevecs Mel Gorman
2017-10-19  9:24   ` Vlastimil Babka
2017-10-18  7:59 ` [PATCH 6/8] mm: Remove cold parameter for release_pages Mel Gorman
2017-10-19  9:26   ` Vlastimil Babka
2017-10-18  7:59 ` [PATCH 7/8] mm, Remove cold parameter from free_hot_cold_page* Mel Gorman
2017-10-19 13:12   ` Vlastimil Babka
2017-10-19 15:43     ` Mel Gorman
2017-10-18  7:59 ` [PATCH 8/8] mm: Remove __GFP_COLD Mel Gorman
2017-10-19 13:18   ` Vlastimil Babka
2017-10-19 13:42   ` Vlastimil Babka
2017-10-19 14:32     ` Mel Gorman
  -- strict thread matches above, loose matches on Subject: below --
2017-10-12  9:30 [PATCH 0/8] Follow-up for speed up page cache truncation Mel Gorman
2017-10-12  9:30 ` [PATCH 1/8] mm, page_alloc: Enable/disable IRQs once when freeing a list of pages Mel Gorman

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