linux-kernel - RE: [PATCH net-next] net: mana: Add page pool for RX buffers

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Message-ID: <PH7PR21MB3116A5F9D82745EF174B4AD5CA3BA@PH7PR21MB3116.namprd21.prod.outlook.com>
Date:   Mon, 17 Jul 2023 18:26:05 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>
CC:     "brouer@...hat.com" <brouer@...hat.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Paul Rosswurm <paulros@...rosoft.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "leon@...nel.org" <leon@...nel.org>,
        Long Li <longli@...rosoft.com>,
        "ssengar@...ux.microsoft.com" <ssengar@...ux.microsoft.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
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        "ast@...nel.org" <ast@...nel.org>,
        Ajay Sharma <sharmaajay@...rosoft.com>,
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        "shradhagupta@...ux.microsoft.com" <shradhagupta@...ux.microsoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>
Subject: RE: [PATCH net-next] net: mana: Add page pool for RX buffers



> -----Original Message-----
> From: Jesper Dangaard Brouer <jbrouer@...hat.com>
> Sent: Friday, July 14, 2023 9:13 AM
> To: Haiyang Zhang <haiyangz@...rosoft.com>; Jesper Dangaard Brouer
> <jbrouer@...hat.com>; Jakub Kicinski <kuba@...nel.org>
> Cc: brouer@...hat.com; linux-hyperv@...r.kernel.org; netdev@...r.kernel.org;
> Dexuan Cui <decui@...rosoft.com>; KY Srinivasan <kys@...rosoft.com>; Paul
> Rosswurm <paulros@...rosoft.com>; olaf@...fle.de; vkuznets@...hat.com;
> davem@...emloft.net; wei.liu@...nel.org; edumazet@...gle.com;
> pabeni@...hat.com; leon@...nel.org; Long Li <longli@...rosoft.com>;
> ssengar@...ux.microsoft.com; linux-rdma@...r.kernel.org;
> daniel@...earbox.net; john.fastabend@...il.com; bpf@...r.kernel.org;
> ast@...nel.org; Ajay Sharma <sharmaajay@...rosoft.com>; hawk@...nel.org;
> tglx@...utronix.de; shradhagupta@...ux.microsoft.com; linux-
> kernel@...r.kernel.org; Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Subject: Re: [PATCH net-next] net: mana: Add page pool for RX buffers
> 
> [You don't often get email from jbrouer@...hat.com. Learn why this is
> important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> On 14/07/2023 14.51, Haiyang Zhang wrote:
> >
> >
> >> -----Original Message-----
> >> From: Jesper Dangaard Brouer <jbrouer@...hat.com>
> >> On 14/07/2023 05.53, Jakub Kicinski wrote:
> >>> On Thu, 13 Jul 2023 14:48:45 +0000 Haiyang Zhang wrote:
> >>>> Add page pool for RX buffers for faster buffer cycle and reduce CPU
> >>>> usage.
> >>>>
> >>>> Get an extra ref count of a page after allocation, so after upper
> >>>> layers put the page, it's still referenced by the pool. We can reuse
> >>>> it as RX buffer without alloc a new page.
> >>>
> >>> Please use the real page_pool API from include/net/page_pool.h
> >>> We've moved past every driver reinventing the wheel, sorry.
> >>
> >> +1
> >>
> >> Quoting[1]: Documentation/networking/page_pool.rst
> >>
> >>    Basic use involves replacing alloc_pages() calls with the
> >> page_pool_alloc_pages() call.
> >>    Drivers should use page_pool_dev_alloc_pages() replacing
> >> dev_alloc_pages().
> >
> > Thank Jakub and Jesper for the reviews.
> > I'm aware of the page_pool.rst doc, and actually tried it before this
> > patch, but I got lower perf. If I understand correctly, we should call
> > page_pool_release_page() before passing the SKB to napi_gro_receive().
> >
> > I found the page_pool_dev_alloc_pages() goes through the slow path,
> > because the page_pool_release_page() let the page leave the pool.
> >
> > Do we have to call page_pool_release_page() before passing the SKB
> > to napi_gro_receive()? Any better way to recycle the pages from the
> > upper layer of non-XDP case?
> >
> 
> Today SKB "upper layers" can recycle page_pool backed packet data/page.
> 
> Just use skb_mark_for_recycle(skb), then you don't need
> page_pool_release_page().

Will do. Thanks a lot!

- Haiyang