From: Cong Wang <xiyou.wangcong@gmail.com>
To: Wanpeng Li <liwp.linux@gmail.com>
Cc: Hugh Dickins <hughd@google.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Minchan Kim <minchan@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] swap: fix shmem swapping when more than 8 areas
Date: Sat, 16 Jun 2012 14:10:56 +0800 [thread overview]
Message-ID: <CAM_iQpXPH2SgjKbj1g5azcddusBmQ0CDvDz_RJe2r2HSTo51yA@mail.gmail.com> (raw)
In-Reply-To: <20120616045637.GA2331@kernel>
On Sat, Jun 16, 2012 at 12:56 PM, Wanpeng Li <liwp.linux@gmail.com> wrote:
>>-#define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT)
>>+#define SWP_TYPE_SHIFT(e) ((sizeof(e.val) * 8) - \
>>+ (MAX_SWAPFILES_SHIFT + RADIX_TREE_EXCEPTIONAL_SHIFT))
>
> Hi Hugh,
>
> Since SHIFT == MAX_SWAPFILES_SHIFT + RADIX_TREE_EXCEPTIONAL_SHIFT == 7
> and the low two bits used for radix_tree, the available swappages number
> based of 32bit architectures reduce to 2^(32-7-2) = 32GB?
>
The lower two bits are in the 7 bits you calculated,
so it is 2^(32-7), not 2^(32-7-2)
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next prev parent reply other threads:[~2012-06-16 6:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-16 0:55 Hugh Dickins
2012-06-16 4:56 ` Wanpeng Li
2012-06-16 6:10 ` Cong Wang [this message]
2012-06-16 10:05 ` Hugh Dickins
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