From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 1 Dec 2005 15:57:11 -0200 From: Marcelo Tosatti Subject: Re: Better pagecache statistics ? Message-ID: <20051201175711.GA17169@dmt.cnet> References: <1133377029.27824.90.camel@localhost.localdomain> <20051201152029.GA14499@dmt.cnet> <1133452790.27824.117.camel@localhost.localdomain> <1133453411.2853.67.camel@laptopd505.fenrus.org> <20051201170850.GA16235@dmt.cnet> <1133457315.21429.29.camel@localhost.localdomain> <1133457700.2853.78.camel@laptopd505.fenrus.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1133457700.2853.78.camel@laptopd505.fenrus.org> Sender: owner-linux-mm@kvack.org Return-Path: To: Arjan van de Ven Cc: Badari Pulavarty , linux-mm , lkml List-ID: 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org