I have a program that needs to read through many files at the same time that are filemapped. In an attempt to get the system to fetch the data before it is needed, I am calling madvise with MADV_SEQUENTIAL on each file mapping. However when it runs, this seems to have little effect. Instead the program runs at 100% cpu for a bit without any disk activity whatsoever, and then stops as it fetches the next chunks from the disk. The number of mapped files can exceed 1000 which I suspect is part of the problem. Am I doing something wrong, or is a better way of telling the system to start fetching the next chunk of each file before it is actually needed, preferably in chunks of a few MB or so.
getting MADV_SEQUENTIAL in freebsd to read ahead
47 Views Asked by camelccc At
1
There are 1 best solutions below
Related Questions in C
- How to call a C language function from x86 assembly code?
- What does: "char *argv[]" mean?
- User input sanitization program, which takes a specific amount of arguments and passes the execution to a bash script
- How to crop a BMP image in half using C
- How can I get the difference in minutes between two dates and hours?
- Why will this code compile although it defines two variables with the same name?
- Compiling eBPF program in Docker fails due to missing '__u64' type
- Why can't I use the file pointer after the first read attempt fails?
- #include Header files in C with definition too
- OpenCV2 on CLion
- What is causing the store latency in this program?
- How to refer to the filepath of test data in test sourcecode?
- 9 Digit Addresses in Hexadecimal System in MacOS
- My server TCP doesn't receive messages from the client in C
- Printing the characters obtained from the array s using printf?
Related Questions in FREEBSD
- Is it safe to assume 8-bit char on Linux and FreeBSD, based on POSIX?
- How can I switch from clang11 to clang14 on freebsd?
- How do I make HTTPS server pool processes work with secure SSL connections?
- FreeBSD 14.0, Ruby on Rails deployment issues (gem sqlite3 not installing)
- Compiling go for FreeBSD 13.2 arm
- Need help in understanding the Capsicum capability mode and its effect on getpass()
- configure: error: C compiler cannot create executables ERROR on FreeBSD 14.0-RELEASE
- Simplifying file comparison in a shell script
- Are There Always-Used and Kernel-Specific System Call For BSDs and Linux?
- Cross-compiling on freebsd13.1 with freebsd11.4
- Built-in/portable method of appending string to file via bash without redirection
- Makefile .for and .if expansion
- Not able to connect to remote FreeBSD server from VScode in mac
- Slow query with 3 seconds of execution
- Better performance with sudo "git clone" FreeBSD
Related Questions in FILE-MAPPING
- Filemapping between python and c++: File not found
- How to load (map) thousands of files as fast as possible?
- Solidworks PDM Vault - Save PDF to server location that matches first 3 digits of FileName
- Filemap readding issues
- Need help about MapViewOfFile performance
- merge contents of two files into one file by bash command
- Trouble locking physical memory for shared memory using Windows functions
- getting MADV_SEQUENTIAL in freebsd to read ahead
- How to get the mapped file object name from the objecthandle in C++?
- How to send a bitmap and text data thought processes using file mapping?
- CreateFileMapping size limit in a 64-bit process
- WINAPI Cpp - OpenFileMapping fails with error (2) ERROR_FILE_NOT_FOUND
- SetEndOfFile error 1224: ERROR_USER_MAPPED_FILE, even the file mapping closed successfully
- C++ too many initializer values on GENERIC_READ when creating a file mapping object
- Reading large files on Linux vs Windows (mmap vs CreateFileMapping/MapViewOfFile)
Trending Questions
- UIImageView Frame Doesn't Reflect Constraints
- Is it possible to use adb commands to click on a view by finding its ID?
- How to create a new web character symbol recognizable by html/javascript?
- Why isn't my CSS3 animation smooth in Google Chrome (but very smooth on other browsers)?
- Heap Gives Page Fault
- Connect ffmpeg to Visual Studio 2008
- Both Object- and ValueAnimator jumps when Duration is set above API LvL 24
- How to avoid default initialization of objects in std::vector?
- second argument of the command line arguments in a format other than char** argv or char* argv[]
- How to improve efficiency of algorithm which generates next lexicographic permutation?
- Navigating to the another actvity app getting crash in android
- How to read the particular message format in android and store in sqlite database?
- Resetting inventory status after order is cancelled
- Efficiently compute powers of X in SSE/AVX
- Insert into an external database using ajax and php : POST 500 (Internal Server Error)
Popular Questions
- How do I undo the most recent local commits in Git?
- How can I remove a specific item from an array in JavaScript?
- How do I delete a Git branch locally and remotely?
- Find all files containing a specific text (string) on Linux?
- How do I revert a Git repository to a previous commit?
- How do I create an HTML button that acts like a link?
- How do I check out a remote Git branch?
- How do I force "git pull" to overwrite local files?
- How do I list all files of a directory?
- How to check whether a string contains a substring in JavaScript?
- How do I redirect to another webpage?
- How can I iterate over rows in a Pandas DataFrame?
- How do I convert a String to an int in Java?
- Does Python have a string 'contains' substring method?
- How do I check if a string contains a specific word?
It seems that the man page of madvise on this platform states:
The solution is therefore another thread that reads from the pages about to be accessed and storing the results in a volatile variable, to force the compiler to perform the read. This way the entire problem goes away. MADV_SEQUENTIAL does not seem to work reliably for persuading the OS to perform readahead.