Date: Tue, 16 Dec 2014 11:42:10 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Christoph Lameter <cl@linux.com>
Cc: akpm@linuxfoundation.org, rostedt@goodmis.org,
        linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        linux-mm@kvack.org, penberg@kernel.org,
        Jesper Dangaard Brouer <brouer@redhat.com>
Subject: Re: [PATCH 3/7] slub: Do not use c->page on free
Message-ID: <20141216024210.GB23270@js1304-P5Q-DELUXE>
References: <20141210163017.092096069@linux.com>
 <20141210163033.717707217@linux.com>
 <20141215080338.GE4898@js1304-P5Q-DELUXE>
 <alpine.DEB.2.11.1412150815210.20101@gentwo.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.11.1412150815210.20101@gentwo.org>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org

On Mon, Dec 15, 2014 at 08:16:00AM -0600, Christoph Lameter wrote:
> On Mon, 15 Dec 2014, Joonsoo Kim wrote:
> 
> > > +static bool same_slab_page(struct kmem_cache *s, struct page *page, void *p)
> > > +{
> > > +	long d = p - page->address;
> > > +
> > > +	return d > 0 && d < (1 << MAX_ORDER) && d < (compound_order(page) << PAGE_SHIFT);
> > > +}
> > > +
> >
> > Somtimes, compound_order() induces one more cacheline access, because
> > compound_order() access second struct page in order to get order. Is there
> > any way to remove this?
> 
> I already have code there to avoid the access if its within a MAX_ORDER
> page. We could probably go for a smaller setting there. PAGE_COSTLY_ORDER?

That is the solution to avoid compound_order() call when slab of
object isn't matched with per cpu slab.

What I'm asking is whether there is a way to avoid compound_order() call when slab
of object is matched with per cpu slab or not.

Thanks.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/