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Message-Id: <20090611143122.108468f1.kamezawa.hiroyu@jp.fujitsu.com>
Date: Thu, 11 Jun 2009 14:31:22 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Johannes Weiner <hannes@...xchg.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Rik van Riel <riel@...hat.com>,
Hugh Dickins <hugh.dickins@...cali.org.uk>,
Andi Kleen <andi@...stfloor.org>,
Wu Fengguang <fengguang.wu@...el.com>,
Minchan Kim <minchan.kim@...il.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [patch v3] swap: virtual swap readahead
On Tue, 9 Jun 2009 21:01:28 +0200
Johannes Weiner <hannes@...xchg.org> wrote:
> [resend with lists cc'd, sorry]
>
> +static int swap_readahead_ptes(struct mm_struct *mm,
> + unsigned long addr, pmd_t *pmd,
> + swp_entry_t *entries,
> + unsigned long cluster)
> +{
> + unsigned long window, min, max, limit;
> + spinlock_t *ptl;
> + pte_t *ptep;
> + int i, nr;
> +
> + window = cluster << PAGE_SHIFT;
> + min = addr & ~(window - 1);
> + max = min + cluster;
Johannes, I wonder there is no reason to use "alignment".
I think we just need to read "nearby" pages. Then, this function's
scan range should be
[addr - window/2, addr + window/2)
or some.
And here, too
> + if (!entries) /* XXX: shmem case */
> + return swapin_readahead_phys(entry, gfp_mask, vma, addr);
> + pmin = swp_offset(entry) & ~(cluster - 1);
> + pmax = pmin + cluster;
pmin = swp_offset(entry) - cluster/2.
pmax = swp_offset(entry) + cluster/2.
I'm sorry if I miss a reason for using "alignment".
Thanks,
-Kame
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