On Wed, 2012-05-30 at 11:12 -0400, John Stoffel wrote: > Cong> This is a draft patch of implementing per-file drop caches. > > Interesting. So can I do this from outside a process? I'm a > SysAdmin, so my POV is from noticing, finding and fixing performance > problems when the system is under pressure. Yes, sure, we need to write a utility (or patch an existing one) to do this for you admins. > > Cong> It introduces a new fcntl command F_DROP_CACHES to drop > Cong> file caches of a specific file. The reason is that currently > Cong> we only have a system-wide drop caches interface, it could > Cong> cause system-wide performance down if we drop all page caches > Cong> when we actually want to drop the caches of some huge file. > > How can I tell how much cache is used by a file? And what is the > performance impact of this when run on a busy system? And what does > this patch buy us since I figure the VM should already be dropping > caches once the system comes under mem pressure... > AFAIK, we don't export such information to user-space, we only have system-wide statistics. Keiichi (in Cc) once wrote a patch to implement page cache tracepoint: http://marc.info/?l=linux-mm&m=131102496904326&w=3 but the patches are still not in upstream. Thanks! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>