ext4 | 易学教程

Intel NVMe drive Performance degradation with xfs filesystem with sector size other than 4096

阅读更多关于 Intel NVMe drive Performance degradation with xfs filesystem with sector size other than 4096

问题 I am working with NVMe card on linux(Ubuntu 14.04). I am finding some performance degradation for Intel NVMe card when formatted with xfs file system with its default sector size(512). or any other sector size less than 4096. In the experiment I formatted the card with xfs filesystem with default options. I tried running fio with 64k block size on an arm64 platform with 64k page size. This is the command used fio --rw=randread --bs=64k --ioengine=libaio --iodepth=8 --direct=1 --group

Linux AIO: Poor Scaling

阅读更多关于 Linux AIO: Poor Scaling

问题 I am writing a library that uses the Linux asynchronous I/O system calls, and would like to know why the io_submit function is exhibiting poor scaling on the ext4 file system. If possible, what can I do to get io_submit not to block for large IO request sizes? I already do the following (as described here): Use O_DIRECT . Align the IO buffer to a 512-byte boundary. Set the buffer size to a multiple of the page size. In order to observe how long the kernel spends in io_submit , I ran a test in

Storing & accessing up to 10 million files in Linux

阅读更多关于 Storing & accessing up to 10 million files in Linux

问题 I'm writing an app that needs to store lots of files up to approx 10 million. They are presently named with a UUID and are going to be around 4MB each but always the same size. Reading and writing from/to these files will always be sequential. 2 main questions I am seeking answers for: 1) Which filesystem would be best for this. XFS or ext4? 2) Would it be necessary to store the files beneath subdirectories in order to reduce the numbers of files within a single directory? For question 2, I

What is the maximum number of subdirectories allowed in Ext4? [closed]

阅读更多关于 What is the maximum number of subdirectories allowed in Ext4? [closed]

问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 years ago . I am considering moving my ext3 partition to ext4 in order to overcome the 32000 subdirectory limit. I have seen two different numbers thrown around about the limits of ext4, both from reputable sources: Limit of 64,000: ext4.wiki.kernel.org SO ServerFault Unlimited: Kernel Newbies Kernel.org SO SuperUser What

How can I access file by inode on Linux

阅读更多关于 How can I access file by inode on Linux

问题 is there any userspace API or third-party kernel module that can help to access file by inode on Linux? I'm trying to implement something like: int read_file_by_ino(int ino, int pos, int size, char* buf); int write_file_by_ino(int ino, int pos, int size, const char* buf); int readdir_by_ino(...); int stat_by_ino(...); ... The program is expected to run under root user, so there's no security requirement to do permission checking. 回答1: I found the question connected concerning similar topic

what is the max files per directory in EXT4?

阅读更多关于 what is the max files per directory in EXT4?

问题 What is the limit of EXT4, what i found is only EXT3, and other links only suppositions and not a real number? Can you please provide me: max number per directory, max size? 回答1: It depends upon the MKFS parameters used during the filesystem creation. Different Linux flavors have different defaults, so it's really impossible to answer your question definitively. 回答2: Follow-up on @Curt's answer. The creation parameters can determine the number of inodes, and that's what can limit you in the

Is lseek() O(1) complexity?

阅读更多关于 Is lseek() O(1) complexity?

问题 I know that my question has an answer here: QFile seek performance. But I am not completely satisfied with the answer. Even after looking at the following implementation of generic_file_llseek() for ext4, I can't seem to understand how can the complexity be measured. /** * generic_file_llseek - generic llseek implementation for regular files * @file: file structure to seek on * @offset: file offset to seek to * @origin: type of seek * * This is a generic implemenation of ->llseek useable for

How can I access file by inode on Linux

阅读更多关于 How can I access file by inode on Linux

is there any userspace API or third-party kernel module that can help to access file by inode on Linux? I'm trying to implement something like: int read_file_by_ino(int ino, int pos, int size, char* buf); int write_file_by_ino(int ino, int pos, int size, const char* buf); int readdir_by_ino(...); int stat_by_ino(...); ... The program is expected to run under root user, so there's no security requirement to do permission checking. Luke I found the question connected concerning similar topic here . Summarizing, check out those commands: find /path/to/mountpoint -inum <inode number> sudo debugfs

what is the max files per directory in EXT4?

阅读更多关于 what is the max files per directory in EXT4?

What is the limit of EXT4, what i found is only EXT3 , and other links only suppositions and not a real number? Can you please provide me: max number per directory, max size? It depends upon the MKFS parameters used during the filesystem creation. Different Linux flavors have different defaults, so it's really impossible to answer your question definitively. Follow-up on @Curt's answer. The creation parameters can determine the number of inodes, and that's what can limit you in the end. df 's -i switch gives you inode info. (env)somesone@somewhere:/$ df -iT Filesystem Type Inodes IUsed IFree

Why does Python give “OSError: [Errno 36] File name too long” for filename shorter than filesystem's limit?

阅读更多关于 Why does Python give “OSError: [Errno 36] File name too long” for filename shorter than filesystem's limit?

问题 The following code yields an unexpected exception: open("52bbe674cdc81d4140099b84fa69eea4249bcceee75bcbe4838d911ab076547cfdad3c1c5197752a98e5525fe76613dbe52dcdb1a9a397669babce0f101d010142cffa000000.csv", "w") OSError: [Errno 36] File name too long: '52bbe674cdc81d4140099b84fa69eea4249bcceee75bcbe4838d911ab076547cfdad3c1c5197752a98e5525fe76613dbe52dcdb1a9a397669babce0f101d010142cffa000000.csv' This is unexpected because my filesystem is ext4 which (according to Wikipedia) has a 255 byte