linux-kernel - Re: [PATCH bpf-next v3] docs/bpf: Add LRU internals description and graph

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Date:   Mon, 13 Mar 2023 12:18:12 -0700
From:   Joe Stringer <joe@...valent.com>
To:     Bagas Sanjaya <bagasdotme@...il.com>
Cc:     bpf@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, ast@...nel.org, corbet@....net,
        martin.lau@...ux.dev, maxtram95@...il.com
Subject: Re: [PATCH bpf-next v3] docs/bpf: Add LRU internals description and graph

On Sun, Mar 12, 2023 at 8:54 PM Bagas Sanjaya <bagasdotme@...il.com> wrote:
>
> On Sun, Mar 12, 2023 at 12:05:59PM -0700, Joe Stringer wrote:
> > +Even if an LRU node may be acquired, maps of type ``BPF_MAP_TYPE_LRU_HASH``
> > +may fail to insert the entry into the map if other CPUs are heavily contending
> > +on the global hashmap lock.
>
> "Even if an LRU node can be acquired, ..."

Ack.

> > +
> > +This algorithm is described visually in the following diagram. See the
> > +description in commit 3a08c2fd7634 ("bpf: LRU List") for a full explanation of
> > +the corresponding operations:
> > +
> > +.. kernel-figure::  map_lru_hash_update.dot
> > +   :alt:    Diagram outlining the LRU eviction steps taken during map update
> > +
> > +   LRU hash eviction during map update for ``BPF_MAP_TYPE_LRU_HASH`` and
> > +   variants
> > +
> > <snipped> ...
> > +The dot file source for the above figure uses internal kernel function names
> > +for the node names in order to make the corresponding logic easier to find.
>
> Shouldn't the figure note above be in :alt:?

Do you mean alt or caption? Alt will hide the information from most developers.

> Otherwise LGTM.

Thanks for the review!