Question
Answer and Explanation
The command "drop clean buffers" (often seen as sync; echo 3 > /proc/sys/vm/drop_caches on Linux systems) is used to clear the system's page cache, dentries, and inodes. While it might seem like a way to free up memory, its use is generally discouraged in most everyday scenarios. Here’s why:
1. How It Works: This command forces the system to drop cached data, which includes frequently accessed file data, directories and file system metadata. By doing so, the OS needs to reread data from storage the next time it's needed, which can slow things down.
2. Potential Performance Hit: When you clear the caches, the system has to rebuild them the next time you access the same data. This results in a performance hit due to increased I/O operations. For example, if you're working on a large project and clear caches, loading the same files again will be significantly slower.
3. Automatic Cache Management: Modern operating systems are designed to automatically manage the cache efficiently. They usually decide what to cache and when to release memory based on system activity. Interfering with this mechanism can be counterproductive, and force unnecessary disk reads when they are not needed.
4. Specific Use Cases (But Still Cautious): There are very few scenarios where this command can be helpful, mainly when benchmarking storage devices or observing memory usage in isolated cases. For instance, if you're measuring the raw performance of a disk without any caching effects. However, even in these situations, it should be done with caution and never be part of your routine.
5. Debugging Situations: If you're working on debugging an application that is behaving unexpectedly (eg. not reading the latest files from the file system), it might be necessary to check if caches are to blame. This is a very rare case, and you should thoroughly check your code before running this command. Running this command in this situation might temporarily alleviate the symptoms but does not solve the actual issue.
6. Alternative Solutions: If you're experiencing memory pressure, you should explore better alternatives such as closing unnecessary applications, checking for memory leaks, and using tools like htop or top to understand what is consuming resources, before considering dropping caches.
In summary, running the "drop clean buffers" command is rarely a good idea for day-to-day use. It's primarily for very specific debugging or testing cases and is not an efficient solution for improving overall system performance. It’s more likely to negatively affect user experience. Let the OS handle memory management unless you have a specific, technical and controlled reason to do otherwise.