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From: Andi Kleen <andi@firstfloor.org>
To: Vitaly Wool <vitalywool@gmail.com>
Cc: Linux-MM <linux-mm@kvack.org>,
	linux-kernel@vger.kernel.org, Dan Streetman <ddstreet@ieee.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andi Kleen <andi@firstfloor.org>
Subject: Re: [PATCH/RFC v2] z3fold: use per-page read/write lock
Date: Tue, 8 Nov 2016 07:08:00 -0800	[thread overview]
Message-ID: <20161108150800.GL26852@two.firstfloor.org> (raw)
In-Reply-To: <20161108135834.d0b57fa435393c64f358980a@gmail.com>

On Tue, Nov 08, 2016 at 01:58:34PM +0100, Vitaly Wool wrote:
> Most of z3fold operations are in-page, such as modifying z3fold
> page header or moving z3fold objects within a page. Taking
> per-pool spinlock to protect per-page objects is therefore
> suboptimal, and the idea of having a per-page spinlock (or rwlock)
> has been around for some time. However, adding one directly to the
> z3fold header makes the latter quite big on some systems so that
> it won't fit in a signle chunk.
> 
> This patch implements spinlock-based per-page locking mechanism
> which is lightweight enough to fit into the z3fold header.
> 
> Changes from v1 [1]:
> - custom locking mechanism changed to spinlocks
> - no read/write locks, just per-page spinlock

Looks good.

BTW the spinlock could still grow when debug options  like
lockdep are enabled. So something would still need to be done about
that BUILD_BUG_ON(). Otherwise would need to force a raw spin lock.

-Andi

      reply	other threads:[~2016-11-08 15:08 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-11-08 12:58 [PATCH/RFC v2] z3fold: use per-page read/write lock Vitaly Wool
2016-11-08 15:08 ` Andi Kleen [this message]

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