Re: Page allocator order-0 optimizations merged

[Pankaj Gupta <pagupta@redhat.com>]

> 
> On Mon, Mar 27, 2017 at 02:39:47PM +0200, Jesper Dangaard Brouer wrote:
> > On Mon, 27 Mar 2017 10:55:14 +0200
> > Jesper Dangaard Brouer <brouer@redhat.com> wrote:
> > 
> > > A possible solution, would be use the local_bh_{disable,enable} instead
> > > of the {preempt_disable,enable} calls.  But it is slower, using numbers
> > > from [1] (19 vs 11 cycles), thus the expected cycles saving is 38-19=19.
> > > 
> > > The problematic part of using local_bh_enable is that this adds a
> > > softirq/bottom-halves rescheduling point (as it checks for pending
> > > BHs).  Thus, this might affects real workloads.
> > 
> > I implemented this solution in patch below... and tested it on mlx5 at
> > 50G with manually disabled driver-page-recycling.  It works for me.
> > 
> > To Mel, that do you prefer... a partial-revert or something like this?
> > 
> 
> If Tariq confirms it works for him as well, this looks far safer patch
> than having a dedicate IRQ-safe queue. Your concern about the BH
> scheduling point is valid but if it's proven to be a problem, there is
> still the option of a partial revert.

I also feel the same.

Thanks,
Pankaj

> 
> --
> Mel Gorman
> SUSE Labs
> 

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