From: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
To: Nick Piggin <npiggin@suse.de>
Cc: Linux Memory Management <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Hugh Dickins <hugh@veritas.com>, Andrew Morton <akpm@osdl.org>,
Andrea Arcangeli <andrea@suse.de>,
Linus Torvalds <torvalds@osdl.org>,
David Miller <davem@davemloft.net>
Subject: Re: [patch 3/3] mm: PageActive no testset
Date: Thu, 19 Jan 2006 14:52:22 -0200 [thread overview]
Message-ID: <20060119165222.GC4418@dmt.cnet> (raw)
In-Reply-To: <20060119145008.GA20126@wotan.suse.de>
On Thu, Jan 19, 2006 at 03:50:08PM +0100, Nick Piggin wrote:
> Hi Marcelo,
>
> On Wed, Jan 18, 2006 at 12:13:46PM -0200, Marcelo Tosatti wrote:
> > Hi Nick,
> >
> > On Wed, Jan 18, 2006 at 11:40:58AM +0100, Nick Piggin wrote:
> > > PG_active is protected by zone->lru_lock, it does not need TestSet/TestClear
> > > operations.
> >
> > page->flags bits (including PG_active and PG_lru bits) are touched by
> > several codepaths which do not hold zone->lru_lock.
> >
> > AFAICT zone->lru_lock guards access to the LRU list, and no more than
> > that.
> >
>
> Yep.
>
> > Moreover, what about consistency of the rest of page->flags bits?
> >
>
> That's OK, set_bit and clear_bit are atomic as well, they just don't
> imply memory barriers and can be implemented a bit more simply.
Indeed!
> The test-set / test-clear operations also kind of imply that it is
> being used for locking or without other synchronisation (usually).
Non-atomic versions such as __ClearPageLRU()/__ClearPageActive() are
not usable, though.
PPC:
static __inline__ void __clear_bit(unsigned long nr,
volatile unsigned long *addr)
{
unsigned long mask = BITOP_MASK(nr);
unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);
*p &= ~mask;
}
next prev parent reply other threads:[~2006-01-19 18:53 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-18 10:40 [patch 0/4] mm: de-skew page refcount Nick Piggin
2006-01-18 10:40 ` [patch 1/4] mm: page refcount use atomic primitives Nick Piggin
2006-01-18 10:40 ` [patch 2/4] mm: PageLRU no testset Nick Piggin
2006-01-19 17:48 ` Nikita Danilov
2006-01-19 18:10 ` Nick Piggin
2006-01-18 10:40 ` [patch 3/3] mm: PageActive " Nick Piggin
2006-01-18 14:13 ` Marcelo Tosatti
2006-01-19 14:50 ` Nick Piggin
2006-01-19 16:52 ` Marcelo Tosatti [this message]
2006-01-19 20:02 ` Nick Piggin
2006-01-19 21:41 ` Marcelo Tosatti
2006-01-18 10:41 ` [patch 4/4] mm: less atomic ops Nick Piggin
2006-01-18 16:38 ` [patch 0/4] mm: de-skew page refcount Linus Torvalds
2006-01-18 17:05 ` Nick Piggin
2006-01-18 19:27 ` Linus Torvalds
2006-01-19 14:00 ` Nick Piggin
2006-01-19 16:36 ` Linus Torvalds
2006-01-19 17:06 ` Nick Piggin
2006-01-19 17:27 ` Linus Torvalds
2006-01-19 17:38 ` Nick Piggin
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