netdev - Re: [net-next v8 1/4] page_pool: Add allocation stats

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Message-ID: <20220301235031.ryy4trywlc3bmnpx@sx1>
Date:   Tue, 1 Mar 2022 15:50:31 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     Joe Damato <jdamato@...tly.com>
Cc:     netdev@...r.kernel.org, kuba@...nel.org,
        ilias.apalodimas@...aro.org, davem@...emloft.net, hawk@...nel.org,
        ttoukan.linux@...il.com, brouer@...hat.com, leon@...nel.org,
        linux-rdma@...r.kernel.org, saeedm@...dia.com
Subject: Re: [net-next v8 1/4] page_pool: Add allocation stats

On 01 Mar 14:10, Joe Damato wrote:
>Add per-pool statistics counters for the allocation path of a page pool.
>These stats are incremented in softirq context, so no locking or per-cpu
>variables are needed.
>
>This code is disabled by default and a kernel config option is provided for
>users who wish to enable them.
>

Sorry for the late review Joe,

Why disabled by default ? if your benchmarks showed no diff.

IMHO If we believe in this, we should have it enabled by default.

>The statistics added are:
>	- fast: successful fast path allocations
>	- slow: slow path order-0 allocations
>	- slow_high_order: slow path high order allocations
>	- empty: ptr ring is empty, so a slow path allocation was forced.
>	- refill: an allocation which triggered a refill of the cache
>	- waive: pages obtained from the ptr ring that cannot be added to
>	  the cache due to a NUMA mismatch.
>

Let's have this documented under kernel documentation.
https://docs.kernel.org/networking/page_pool.html

I would also mention the kconfig and any user knobs APIs introduced in
this series