nocache - don't use Linux page cache on given command
nocache [-n <n>] command [argument...]
- -n <n> "Set number of fadvise calls"
- Execute the `posix_fadvise` system call <n> times in a row. Depending on your machine, this might give better results (use it if in your tests `nocache` fails to eradicate pages from cache properly).
The `nocache` tool tries to minimize the effect an application has on the Linux file system cache. This is done by intercepting the `open` and `close` system calls and calling `posix_fadvise` with the `POSIX_FADV_DONTNEED` parameter. Because the library remembers which pages (ie., 4K-blocks of the file) were already in file system cache when the file was opened, these will not be marked as "don't need", because other applications might need that, although they are not actively used (think: hot standby).
Use case: backup processes that should not interfere with the present state of the cache.