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

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Date:   Fri, 14 Jul 2023 12:51:41 +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>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        Ajay Sharma <sharmaajay@...rosoft.com>,
        "hawk@...nel.org" <hawk@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "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>
> 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?

Thanks,
- Haiyang