alamb commented on code in PR #6336: URL: https://github.com/apache/arrow-rs/pull/6336#discussion_r1773694821
########## arrow/examples/allocator_api.rs: ########## @@ -0,0 +1,115 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +//! Customizing [`Allocator`] for Arrow Array's underlying [`MutableBuffer`]. +//! +//! This module requires the `allocator_api` feature and a nightly channel Rust toolchain. + +#![cfg_attr(feature = "allocator_api", feature(allocator_api))] + +fn main() { + demo(); +} + +#[cfg(not(feature = "allocator_api"))] +fn demo() { + println!("This example requires the `allocator_api` feature to be enabled."); +} + +#[cfg(feature = "allocator_api")] +mod allocator { + /// A simple allocator tracker that records and reports memory usage. + #[derive(Clone)] + pub struct AllocatorTracker<A> + where + A: std::alloc::Allocator + Clone, + { + usage: std::sync::Arc<std::sync::atomic::AtomicIsize>, + alloc: A, + } + + impl<A> AllocatorTracker<A> + where + A: std::alloc::Allocator + Clone, + { + pub fn new(alloc: A) -> Self { + Self { + usage: std::sync::Arc::new(std::sync::atomic::AtomicIsize::new(0)), + alloc, + } + } + + pub fn report_usage(&self) -> isize { + self.usage.load(std::sync::atomic::Ordering::Relaxed) + } + } + + unsafe impl<A> std::alloc::Allocator for AllocatorTracker<A> + where + A: std::alloc::Allocator + Clone, + { + fn allocate( + &self, + layout: std::alloc::Layout, + ) -> Result<std::ptr::NonNull<[u8]>, std::alloc::AllocError> { + let size = layout.size(); + self.usage + .fetch_add(size as isize, std::sync::atomic::Ordering::Relaxed); + + self.alloc.allocate(layout) + } + + unsafe fn deallocate(&self, ptr: std::ptr::NonNull<u8>, layout: std::alloc::Layout) { + let size = layout.size(); + self.usage + .fetch_sub(size as isize, std::sync::atomic::Ordering::Relaxed); + + self.alloc.deallocate(ptr, layout) + } + } +} + +#[cfg(feature = "allocator_api")] +fn demo() { + use arrow::buffer::MutableBuffer; + use std::alloc::Global; + + let allocator_tracker = allocator::AllocatorTracker::new(Global); + + // Creates a mutable buffer with customized allocator + let mut buffer = + MutableBuffer::<allocator::AllocatorTracker<std::alloc::Global>>::with_capacity_in( + 10, + allocator_tracker.clone(), + ); + println!( + "Current memory usage: {} bytes", + allocator_tracker.report_usage() + ); + + // Inherits allocator from Vec + let vector = Vec::<u8, allocator::AllocatorTracker<std::alloc::Global>>::with_capacity_in( + 100, + allocator_tracker.clone(), + ); + let mut buffer = MutableBuffer::from(vector); Review Comment: This is very cool -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
