Re: [Libguestfs] [nbdkit PATCH v3 14/15] todo: Mention possibility of caching .can_FOO callbacks

Recent patches clarified documentation to point out that within the life of a single connection, the .can_FOO helpers should return consistent results, and that callers may cache those results. But at least in the case of .can_fua, we aren't really caching things; depending on the overhead involved, calling out to the plugin's .can_fua on every .pwrite with FUA requested may be noticeable overhead compared to caching it. Any cache must not be a static variable, as it can differ between connections. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- TODO | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/TODO b/TODO index b6fb0b1..1e0f483 100644 --- a/TODO +++ b/TODO @@ -40,6 +40,10 @@ General ideas for improvements ones like offset) can fail to initialize if they can't guarantee strict alignment and don't want to deal with bounce buffers. +* Add per-connection caching of .can_FOO callbacks (we already have + some: .can_write is only called once, but .can_fua is called on + every request with the FUA flag set). + Suggestions for plugins -----------------------