Re: [PATCH for-rc 1/5] IB/hfi1: Fix WQ_MEM_RECLAIM warning

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On Wed, Mar 27, 2019 at 08:25:17AM -0700, Tejun Heo (tj@xxxxxxxxxx) wrote:
> Hello,
>
> On Tue, Mar 26, 2019 at 08:55:09PM +0000, Marciniszyn, Mike wrote:
> > The latter is the ipoib wq that conflicts with our non-WQ_MEM_RECLAIM.  This seems excessive and pretty gratuitous.
> >
> > Tejun, what does "mem reclaim" really mean and when should it be used?
>
> That it may be depended during memory reclaim.
>
> > I was assuming that since we are freeing QP kernel memory held by user mode programs that could be oom killed, we need the flag.
>
> If it can't block memory reclaim, it doesn't need the flag.  Just in
> case, if a workqueue is used to issue block IOs, it is depended upon
> for memory reclaim as writeback and swap-outs are critical parts of
> memory reclaim.

It looks like WQ_MEM_RECLAIM is needed for IPoIB, because if NFS runs
over IPoIB, it will do those types of IOs.

Thanks

>
> Thanks.
>
> --
> tejun

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