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

From: Joe Stringer <joe@isovalent.com>
To: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: bpf@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, ast@kernel.org, corbet@lwn.net,
	martin.lau@linux.dev, maxtram95@gmail.com
Subject: Re: [PATCH bpf-next v3] docs/bpf: Add LRU internals description and graph
Date: Mon, 13 Mar 2023 12:18:12 -0700	[thread overview]
Message-ID: <CADa=Ryyp10=ki5ctVTVbeUFy23uyRbi+ZgJE5JpxX3UFWvQcyw@mail.gmail.com> (raw)
In-Reply-To: <ZA6ecdQl3STWVAH6@debian.me>

On Sun, Mar 12, 2023 at 8:54 PM Bagas Sanjaya <bagasdotme@gmail.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!