![]() ![]() When a process reads sequentially a file the kernel starts reading some data in advance to reduce the amount of time that a process have to wait for data to be available, so this parameter sets the maximum amount of data that the kernel reads ahead for a single file. Changing the file system is one of them, as it's explained in this page: High performance SD card tuning using the EXT4 file system Readahead Sometimes tuning these parameters is not sufficient and more aggressive decisions have to be made. It's recommendable to modify only one of the previous tuning parameters. Default: 3000Įcho 200 > /proc/sys/vm/dirty_expire_centisecs This defines the interval between writeback operations. When this is exceeded, applications that want to write to the pagecache are blocked and start performing writeback as well. When the amount of dirty pagecache exceeds this percentage, writeback threads start writing back dirty memory. If dirty data reaches a critical percentage of RAM, processes begin to be throttled to prevent dirty data exceeding this threshold. While writing files, there are cache pages becoming dirty, each amount of time or once dirty memory reaches a percentage of RAM, the kernel starts doing writeback. Tuning Write/Read memory operations Writeback The references bellow offer useful information describing how Linux operating system manages system resources, important performance metrics that are needed to quantify system performance and how to tune I/O performance, task scheduler, memory management subsystem and network. Tuning Linux kernel is a challenging task specially because it requires in-depth understanding of the hardware, operating system, and application. There are several parameters and criteria available to tune the Linux kernel according with specific application requirements. ![]() Usually the biggest bottlenecks for processes performance are the I/O operations mainly on memory, disk and network. ![]()
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