netdev - Re: [PATCH] net: core: page_pool: add user refcnt and reintroduce page_pool

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Message-ID: <20190702202907.15fb30ce@carbon>
Date:   Tue, 2 Jul 2019 20:29:07 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
Cc:     netdev@...r.kernel.org,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        grygorii.strashko@...com, jakub.kicinski@...ronome.com,
        daniel@...earbox.net, john.fastabend@...il.com, ast@...nel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        brouer@...hat.com
Subject: Re: [PATCH] net: core: page_pool: add user refcnt and reintroduce
 page_pool_destroy

On Tue, 2 Jul 2019 18:21:13 +0300
Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org> wrote:

> On Tue, Jul 02, 2019 at 05:10:29PM +0200, Jesper Dangaard Brouer wrote:
> >On Tue, 2 Jul 2019 17:56:13 +0300
> >Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org> wrote:
> >  
> >> On Tue, Jul 02, 2019 at 04:52:30PM +0200, Jesper Dangaard Brouer wrote:  
> >> >On Tue, 2 Jul 2019 17:44:27 +0300
> >> >Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org> wrote:
> >> >  
> >> >> On Tue, Jul 02, 2019 at 04:31:39PM +0200, Jesper Dangaard Brouer wrote:  
> >> >> >From: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> >> >> >
> >> >> >Jesper recently removed page_pool_destroy() (from driver invocation) and
> >> >> >moved shutdown and free of page_pool into xdp_rxq_info_unreg(), in-order to
> >> >> >handle in-flight packets/pages. This created an asymmetry in drivers
> >> >> >create/destroy pairs.
> >> >> >
> >> >> >This patch add page_pool user refcnt and reintroduce page_pool_destroy.
> >> >> >This serves two purposes, (1) simplify drivers error handling as driver now
> >> >> >drivers always calls page_pool_destroy() and don't need to track if
> >> >> >xdp_rxq_info_reg_mem_model() was unsuccessful. (2) allow special cases
> >> >> >where a single RX-queue (with a single page_pool) provides packets for two
> >> >> >net_device'es, and thus needs to register the same page_pool twice with two
> >> >> >xdp_rxq_info structures.  
> >> >>
> >> >> As I tend to use xdp level patch there is no more reason to mention (2) case
> >> >> here. XDP patch serves it better and can prevent not only obj deletion but also
> >> >> pool flush, so, this one patch I could better leave only for (1) case.  
> >> >
> >> >I don't understand what you are saying.
> >> >
> >> >Do you approve this patch, or do you reject this patch?
> >> >  
> >> It's not reject, it's proposition to use both, XDP and page pool patches,
> >> each having its goal.  
> >
> >Just to be clear, if you want this patch to get accepted you have to
> >reply with your Signed-off-by (as I wrote).
> >
> >Maybe we should discuss it in another thread, about why you want two
> >solutions to the same problem.  
> 
> If it solves same problem I propose to reject this one and use this:
> https://lkml.org/lkml/2019/7/2/651

No, I propose using this one, and rejecting the other one.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer