servo/components/style/gecko/global_style_data.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! Global style data

use num_cpus;
use rayon;
use shared_lock::SharedRwLock;
use std::cmp;
use std::env;

/// Global style data
pub struct GlobalStyleData {
    /// How many threads parallel styling can use.
    pub num_threads: usize,

    /// The parallel styling thread pool.
    pub style_thread_pool: Option<rayon::ThreadPool>,

    /// Shared RWLock for CSSOM objects
    pub shared_lock: SharedRwLock,
}

lazy_static! {
    /// Global style data
    pub static ref GLOBAL_STYLE_DATA: GlobalStyleData = {
        let stylo_threads = env::var("STYLO_THREADS")
            .map(|s| s.parse::<usize>().expect("invalid STYLO_THREADS value"));
        let num_threads = match stylo_threads {
            Ok(num) => num,
            _ => cmp::max(num_cpus::get() * 3 / 4, 1),
        };

        let pool = if num_threads <= 1 {
            None
        } else {
            let configuration =
                rayon::Configuration::new().set_num_threads(num_threads);
            let pool = rayon::ThreadPool::new(configuration).ok();
            pool
        };

        GlobalStyleData {
            num_threads: num_threads,
            style_thread_pool: pool,
            shared_lock: SharedRwLock::new(),
        }
    };
}