Log Scheduled Tasks That Take Too Long

// Tasks slower than this many seconds are logged.
$wpide_cron_slow = 3;

add_action( 'init', function () use ( $wpide_cron_slow ) {
    if ( ! wp_doing_cron() ) {
        return;
    }

    foreach ( (array) _get_cron_array() as $time => $hooks ) {
        if ( $time > time() ) {
            break;
        }
        foreach ( array_keys( (array) $hooks ) as $hook ) {
            add_action( $hook, function () use ( $hook ) {
                $GLOBALS['wpide_cron_start'][ $hook ] = microtime( true );
            }, PHP_INT_MIN );
            add_action( $hook, function () use ( $hook, $wpide_cron_slow ) {
                if ( empty( $GLOBALS['wpide_cron_start'][ $hook ] ) ) {
                    return;
                }
                $took = microtime( true ) - $GLOBALS['wpide_cron_start'][ $hook ];
                if ( $took >= $wpide_cron_slow ) {
                    $log            = (array) get_option( 'wpide_slow_cron', array() );
                    $log[ $hook ]   = array( 'time' => round( $took, 2 ), 'when' => time(), 'max' => max( $took, isset( $log[ $hook ]['max'] ) ? (float) $log[ $hook ]['max'] : 0 ) );
                    update_option( 'wpide_slow_cron', array_slice( $log, -50, null, true ), false );
                }
            }, PHP_INT_MAX );
        }
    }
}, 99 );

add_action( 'admin_menu', function () {
    add_management_page( 'Slow Cron Tasks', 'Slow Cron Tasks', 'manage_options', 'wpide-slow-cron', function () {
        $log = (array) get_option( 'wpide_slow_cron', array() );

        echo '<div class="wrap"><h1>Slow Cron Tasks</h1><table class="widefat striped"><thead><tr><th>Hook</th><th>Last run</th><th>Slowest run</th><th>When</th></tr></thead><tbody>';
        if ( ! $log ) {
            echo '<tr><td colspan="4">No slow tasks recorded yet.</td></tr>';
        }
        foreach ( $log as $hook => $row ) {
            printf( '<tr><td><code>%s</code></td><td>%ss</td><td>%ss</td><td>%s</td></tr>', esc_html( $hook ), esc_html( $row['time'] ), esc_html( round( (float) $row['max'], 2 ) ), esc_html( human_time_diff( (int) $row['when'] ) . ' ago' ) );
        }
        echo '</tbody></table></div>';
    } );
} );