netdev - Re: [PATCH net-next v2 4/4] net: hns3: support skb's frag page recycling based on page pool

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Date:   Wed, 8 Sep 2021 08:08:43 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     moyufeng <moyufeng@...wei.com>
Cc:     Yunsheng Lin <linyunsheng@...wei.com>, <davem@...emloft.net>,
        <alexander.duyck@...il.com>, <linux@...linux.org.uk>,
        <mw@...ihalf.com>, <linuxarm@...neuler.org>,
        <yisen.zhuang@...wei.com>, <salil.mehta@...wei.com>,
        <thomas.petazzoni@...tlin.com>, <hawk@...nel.org>,
        <ilias.apalodimas@...aro.org>, <ast@...nel.org>,
        <daniel@...earbox.net>, <john.fastabend@...il.com>,
        <akpm@...ux-foundation.org>, <peterz@...radead.org>,
        <will@...nel.org>, <willy@...radead.org>, <vbabka@...e.cz>,
        <fenghua.yu@...el.com>, <guro@...com>, <peterx@...hat.com>,
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        <hughd@...gle.com>, <jonathan.lemon@...il.com>, <alobakin@...me>,
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        <haokexin@...il.com>, <nogikh@...gle.com>, <elver@...gle.com>,
        <yhs@...com>, <kpsingh@...nel.org>, <andrii@...nel.org>,
        <kafai@...com>, <songliubraving@...com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bpf@...r.kernel.org>,
        <chenhao288@...ilicon.com>
Subject: Re: [PATCH net-next v2 4/4] net: hns3: support skb's frag page
 recycling based on page pool

On Wed, 8 Sep 2021 16:31:40 +0800 moyufeng wrote:
>     After adding page pool to hns3 receiving package process,
> we want to add some debug info. Such as below:
> 
> 1. count of page pool allocate and free page, which is defined
> for pages_state_hold_cnt and pages_state_release_cnt in page
> pool framework.
> 
> 2. pool size、order、nid、dev、max_len, which is setted for
> each rx ring in hns3 driver.
> 
> In this regard, we consider two ways to show these info：
> 
> 1. Add it to queue statistics and query it by ethtool -S.
> 
> 2. Add a file node "page_pool_info" for debugfs, then cat this
> file node, print as below:
> 
> queue_id  allocate_cnt  free_cnt  pool_size  order  nid  dev  max_len
> 000		   xxx       xxx        xxx    xxx  xxx  xxx      xxx
> 001
> 002
> .
> .
> 	
> Which one is more acceptable, or would you have some other suggestion?

Normally I'd say put the stats in ethtool -S and the rest in debugfs
but I'm not sure if exposing pages_state_hold_cnt and
pages_state_release_cnt directly. Those are short counters, and will
very likely wrap. They are primarily meaningful for calculating
page_pool_inflight(). Given this I think their semantics may be too
confusing for an average ethtool -S user.

Putting all the information in debugfs seems like a better idea.