Messages in this thread | | | Date | Thu, 1 Dec 2005 15:57:11 -0200 | From | Marcelo Tosatti <> | Subject | Re: Better pagecache statistics ? |
| |
On Thu, Dec 01, 2005 at 06:21:39PM +0100, Arjan van de Ven wrote: > On Thu, 2005-12-01 at 09:15 -0800, Badari Pulavarty wrote: > > > Most of the issues you mention are null if you move the stats > > > maintenance burden to userspace. > > > > > > The performance impact is also minimized since the hooks > > > (read: overhead) can be loaded on-demand as needed. > > > > > > > The overhead is - going through each mapping/inode in the system > > and dumping out "nrpages" - to get per-file statistics. This is > > going to be expensive, need locking and there is no single list > > we can traverse to get it. I am not sure how to do this.
Can't you add hooks to add_to_page_cache/remove_from_page_cache to record pagecache activity ?
> and worse... you're going to need memory to store the results, either in > kernel or in userspace, and you don't know how much until you're done. > That memory is going to need to be allocated, which in turn changes the > vm state..
Indeed - need to pre-allocate some sensible amount of memory to store the results (relayfs does it for your).
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |