On Thu, Jul 28, 2011 at 2:58 AM, Prateek Sharma <prateeks@xxxxxxxxxxxxxx> wrote: > Hello everyone, > I've been trying to understand the role of the pagecache, starting with > drop_caches and observing what it does. > From my understanding of the code (fs/drop_caches.c) , it walks over all > the open files/inodes, and invalidates all the mapped pages. Stepping up a little, I think you're missing drop_caches_sysctl_handler() in that same file. It is the entry point I believe that implements the userspace ABI defined in Documentation/sysctl/vm.txt. ============================================================== 139 140drop_caches 141 142Writing to this will cause the kernel to drop clean caches, dentries and 143inodes from memory, causing that memory to become free. 144 145To free pagecache: 146 echo 1 > /proc/sys/vm/drop_caches 147To free dentries and inodes: 148 echo 2 > /proc/sys/vm/drop_caches 149To free pagecache, dentries and inodes: 150 echo 3 > /proc/sys/vm/drop_caches 151 152As this is a non-destructive operation and dirty objects are not freeable, the 153user should run `sync' first. 154 155============================================================== Note the corresponding logic in /fs/drop_caches.c that implements the above binary logic. 61 if (sysctl_drop_caches & 1) 62 iterate_supers(drop_pagecache_sb, NULL); 63 if (sysctl_drop_caches & 2) 64 drop_slab(); Greg _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
