Re: [PATCH 0/3] Fix malloc() stall in zone_reclaim() and bring behaviour more in line with expectations V3

From: KOSAKI Motohiro
Date: Tue Jun 16 2009 - 08:09:02 EST

> On Mon, Jun 15, 2009 at 11:01:41AM -0400, Christoph Lameter wrote:
> > On Mon, 15 Jun 2009, Mel Gorman wrote:
> >
> > > > May I ask your worry?
> > > >
> > >
> > > Simply that I believe the intention of PF_SWAPWRITE here was to allow
> > > zone_reclaim() to aggressively reclaim memory if the reclaim_mode allowed
> > > it as it was a statement that off-node accesses are really not desired.
> >
> > Right.
> >
> > > Ok. I am not fully convinced but I'll not block it either if believe it's
> > > necessary. My current understanding is that this patch only makes a difference
> > > if the server is IO congested in which case the system is struggling anyway
> > > and an off-node access is going to be relatively small penalty overall.
> > > Conceivably, having PF_SWAPWRITE set makes things worse in that situation
> > > and the patch makes some sense.
> >
> > We could drop support for RECLAIM_SWAP if that simplifies things.
> >
> I don't think that is necessary. While I expect it's very rarely used, I
> imagine a situation where it would be desirable on a system that had large
> amounts of tmpfs pages but where it wasn't critical they remain in-memory.
> Removing PF_SWAPWRITE would make it less aggressive and if you were
> happy with that, then that would be good enough for me.

I surprised this a bit. I've imazined Christoph never agree to remove it.
Currently, trouble hitting user of mine don't use this feature. Thus, if it can be
removed, I don't need to worry abusing this again and I'm happy.

Mel, Have you seen actual user of this?

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