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Message-ID: <20090316164735.GM24293@csn.ul.ie>
Date: Mon, 16 Mar 2009 16:47:36 +0000
From: Mel Gorman <mel@....ul.ie>
To: Christoph Lameter <cl@...ux-foundation.org>
Cc: Linux Memory Management List <linux-mm@...ck.org>,
Pekka Enberg <penberg@...helsinki.fi>,
Rik van Riel <riel@...hat.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Johannes Weiner <hannes@...xchg.org>,
Nick Piggin <npiggin@...e.de>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Lin Ming <ming.m.lin@...el.com>,
Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 26/35] Use the per-cpu allocator for orders up to
PAGE_ALLOC_COSTLY_ORDER
On Mon, Mar 16, 2009 at 12:26:07PM -0400, Christoph Lameter wrote:
> On Mon, 16 Mar 2009, Mel Gorman wrote:
>
> > -static void free_hot_cold_page(struct page *page, int cold)
> > +static void free_hot_cold_page(struct page *page, int order, int cold)
> > {
> > struct zone *zone = page_zone(page);
> > struct per_cpu_pages *pcp;
> > unsigned long flags;
> > int clearMlocked = PageMlocked(page);
> >
> > + /* SLUB can return lowish-order compound pages that need handling */
> > + if (order > 0 && unlikely(PageCompound(page)))
> > + if (unlikely(destroy_compound_page(page, order)))
> > + return;
> > +
>
> Isnt that also true for stacks and generic network objects ==- 8k?
>
I think they are vanilla high-order pages, not compound pages.
> > again:
> > cpu = get_cpu();
> > - if (likely(order == 0)) {
> > + if (likely(order <= PAGE_ALLOC_COSTLY_ORDER)) {
> > struct per_cpu_pages *pcp;
> > + int batch;
> > + int delta;
> >
> > pcp = &zone_pcp(zone, cpu)->pcp;
> > + batch = max(1, pcp->batch >> order);
> > local_irq_save(flags);
> > if (!pcp->count) {
> > - pcp->count = rmqueue_bulk(zone, 0,
> > - pcp->batch, &pcp->list, migratetype);
> > + delta = rmqueue_bulk(zone, order, batch,
> > + &pcp->list, migratetype);
> > + bulk_add_pcp_page(pcp, order, delta);
> > if (unlikely(!pcp->count))
> > goto failed;
>
> The pcp adds a series of order N pages if an order N alloc occurs and the
> queue is empty?
>
Nope, that would be bad. The calculation of batch is made above and is
batch = max(1, pcp->batch >> order);
so order is taken into account when deciding how many pages to allocate.
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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