linux-kernel - Re: [PATCH 3/5] nfsd: Only set PF_LESS

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Message-ID: <20140512110557.67f2028e@notabene.brown>
Date:	Mon, 12 May 2014 11:05:57 +1000
From:	NeilBrown <neilb@...e.de>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Jan Kara <jack@...e.cz>, Jeff Layton <jlayton@...hat.com>,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Dave Chinner <david@...morbit.com>,
	Mel Gorman <mgorman@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] nfsd: Only set PF_LESS_THROTTLE when really needed.

On Tue, 6 May 2014 16:54:18 -0400 "J. Bruce Fields" <bfields@...ldses.org>
wrote:

> On Wed, Apr 23, 2014 at 12:40:58PM +1000, NeilBrown wrote:
> > PF_LESS_THROTTLE has a very specific use case: to avoid deadlocks
> > and live-locks while writing to the page cache in a loop-back
> > NFS mount situation.
> > 
> > It therefore makes sense to *only* set PF_LESS_THROTTLE in this
> > situation.
> > We now know when a request came from the local-host so it could be a
> > loop-back mount.  We already know when we are handling write requests,
> > and when we are doing anything else.
> > 
> > So combine those two to allow nfsd to still be throttled (like any
> > other process) in every situation except when it is known to be
> > problematic.
> 
> Looks simple enough, ACK.--b.
> 

Thanks.
I'll resend the bits need for just this.

The NFS side need to wait for wait_on_bit improvements which seem to be on a
slow path at the moment.

Thanks,
NeilBrown

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