Linux 7.0 Merges "Significant Improvement" For close_range System Call
([Linux Kernel] 4 Hours Ago
close_range)
- Reference: 0001614107
- News link: https://www.phoronix.com/news/Linux-7.0-Faster-Close-Range
- Source link:
The close_range system call for closing all file descriptors "FDs" in a given range should enjoy a nice speed boost with the in-development [1]Linux 7.0 kernel.
Last week saw all the feature-heavy VFS pull requests that brought [2]nullfs and open_tree_namespace , [3]standardized generic I/O error reporting , non-blocking timestamps, and other improvements. Sent out on Monday were some lingering VFS patches mailed out by Christian Brauner.
Notable with the [4]vfs misc 2 pull is optimizing the close_range system call. The close_range usage drops from O(range size) to O(active FDs) with now being more efficient to provide a "significant improvement" for large range close operations on sparse file descriptor tables. Brauner summed it up as:
"Optimize close_range() from O(range size) to O(active FDs) by using find_next_bit() on the open_fds bitmap instead of linearly scanning the entire requested range. This is a significant improvement for large-range close operations on sparse file descriptor tables."
The close_range system call is used to close all file descriptors in a given range on the system.
Qiliang Yuan of China Telecom who authored this patch had similarly [5]wrote :
"In close_range(), the kernel traditionally performs a linear scan over the [fd, max_fd] range, resulting in O(N) complexity where N is the range size. For processes with sparse FD tables, this is inefficient as it checks many unallocated slots.
This patch optimizes __range_close() by using find_next_bit() on the open_fds bitmap to skip holes. This shifts the algorithmic complexity from O(Range Size) to O(Active FDs), providing a significant performance boost for large-range close operations on sparse file descriptor tables."
The code was merged today to Linux Git. A lot of nice work building up for Linux 7.0.
[1] https://www.phoronix.com/search/Linux+7.0
[2] https://www.phoronix.com/news/Linux-7.0-NULLFS-Namespace
[3] https://www.phoronix.com/news/Linux-7.0-VFS
[4] https://lore.kernel.org/lkml/20260216-vfs-misc-2-v70-fd637c6f249a@brauner/
[5] https://lore.kernel.org/all/20260123081221.659125-1-realwujing@gmail.com/
Last week saw all the feature-heavy VFS pull requests that brought [2]nullfs and open_tree_namespace , [3]standardized generic I/O error reporting , non-blocking timestamps, and other improvements. Sent out on Monday were some lingering VFS patches mailed out by Christian Brauner.
Notable with the [4]vfs misc 2 pull is optimizing the close_range system call. The close_range usage drops from O(range size) to O(active FDs) with now being more efficient to provide a "significant improvement" for large range close operations on sparse file descriptor tables. Brauner summed it up as:
"Optimize close_range() from O(range size) to O(active FDs) by using find_next_bit() on the open_fds bitmap instead of linearly scanning the entire requested range. This is a significant improvement for large-range close operations on sparse file descriptor tables."
The close_range system call is used to close all file descriptors in a given range on the system.
Qiliang Yuan of China Telecom who authored this patch had similarly [5]wrote :
"In close_range(), the kernel traditionally performs a linear scan over the [fd, max_fd] range, resulting in O(N) complexity where N is the range size. For processes with sparse FD tables, this is inefficient as it checks many unallocated slots.
This patch optimizes __range_close() by using find_next_bit() on the open_fds bitmap to skip holes. This shifts the algorithmic complexity from O(Range Size) to O(Active FDs), providing a significant performance boost for large-range close operations on sparse file descriptor tables."
The code was merged today to Linux Git. A lot of nice work building up for Linux 7.0.
[1] https://www.phoronix.com/search/Linux+7.0
[2] https://www.phoronix.com/news/Linux-7.0-NULLFS-Namespace
[3] https://www.phoronix.com/news/Linux-7.0-VFS
[4] https://lore.kernel.org/lkml/20260216-vfs-misc-2-v70-fd637c6f249a@brauner/
[5] https://lore.kernel.org/all/20260123081221.659125-1-realwujing@gmail.com/