netdev - Re: [PATCH] SIW: Object management

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Message-ID: <OF1E676C64.A340B840-ONC12577B7.0049A69D-C12577B7.004DE449@ch.ibm.com>
Date:	Sat, 9 Oct 2010 16:10:46 +0200
From:	Bernard Metzler <BMT@...ich.ibm.com>
To:	Steve Wise <swise@...ngridcomputing.com>
Cc:	linux-rdma@...r.kernel.org, linux-rdma-owner@...r.kernel.org,
	netdev@...r.kernel.org, Roland Dreier <rdreier@...co.com>
Subject: Re: [PATCH] SIW: Object management

<snip>

> > 
> >> the post_send/recv and other functions in your driver are called
> >> directly (almost) by kernel users like NFSRDMA.  These users may be
> >> calling in an interrupt context and thus you cannot block/sleep.
> >>
> >> 
> > OK, very convincing. not a big change since siw_wqe_get/_put()
> > already maintain a list of pre-allocated wqe's (currently for
> > the read.responses).
> > but, would it be ok if the code distinguishes between user
> > land and in-kernel consumers? i would be very happy if we could
> > keep the pre-allocations per user land connection to its very
> > minimum...
> >
> > 
> 
> I think that's ok, but its bending the core locking rules a little I 
> guess.  But the intent is that kernel users can definitely 
> send/recv/poll in interrupt context, so possibly blocking for user mode 
> QPs in on-kernel-bypass operations is probably ok...
> 
i think its best if the code can be optimized this way. i will provide
a patch following down that path soon after i am back from vacation
(next week i am off).
while respecting the specific kernel user requirements, i really want
to keep memory allocations small for user land applications. 

thanks,
bernard.
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