lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 20 Mar 2014 21:33:58 +0000
From:	Mel Gorman <>
To:	Johannes Weiner <>
Cc:	Andrew Morton <>,
	Rik van Riel <>,,
Subject: Re: [patch] mm: page_alloc: spill to remote nodes before waking

On Thu, Mar 20, 2014 at 04:53:36PM -0400, Johannes Weiner wrote:
> On NUMA systems, a node may start thrashing cache or even swap
> anonymous pages while there are still free pages on remote nodes.
> This is a result of 81c0a2bb515f ("mm: page_alloc: fair zone allocator
> policy") and fff4068cba48 ("mm: page_alloc: revert NUMA aspect of fair
> allocation policy").  Before those changes, the allocator would first
> try all allowed zones, including those on remote nodes, before waking
> any kswapds.  But now, the allocator fastpath doubles as the fairness
> pass, which in turn can only consider the local node to prevent remote
> spilling based on exhausted fairness batches alone.  Remote nodes are
> only considered in the slowpath, after the kswapds are woken up.  But
> if remote nodes still have free memory, kswapd should not be woken to
> rebalance the local node or it may thrash cash or swap prematurely.
> Fix this by adding one more unfair pass over the zonelist that is
> allowed to spill to remote nodes after the local fairness pass fails
> but before entering the slowpath and waking the kswapds.
> This also gets rid of the GFP_THISNODE exemption from the fairness
> protocol because the unfair pass is no longer tied to kswapd, which
> GFP_THISNODE is not allowed to wake up.
> However, because remote spills can be more frequent now - we prefer
> them over local kswapd reclaim - the allocation batches on remote
> nodes could underflow more heavily.  When resetting the batches, use
> atomic_long_read() directly instead of zone_page_state() to calculate
> the delta as the latter filters negative counter values.
> Signed-off-by: Johannes Weiner <>
> Cc: <> [3.12+]

Acked-by: Mel Gorman <>

Mel Gorman
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists