On Thu Oct 15 12:56:00 EDT 2009, ma...@digitalwest.net wrote: ... > At what layer(s) does page cache come into play? I know the gist of > how it functions but not the dirty details. I thought it only came > into play when using a filesystem? > For example, if the controllers shared a block device using vbladed, > running with direct io wouldn't ensure consistency on both controllers?
Even when you're not using a filesystem you have caching going on, unless you request otherwise. You can see the difference with a "dd" that has the option for doing O_DIRECT. With that option, you're bypassing the page cache. Without it, you will notice that there's lots of writing at first but then it slows down to a crawl when the system finally decides to flush out the data from all the pages in RAM that have been dirtied. I guess mkfs is a more obvious one, since it has a progress meter, but you can get progress from dd via SIGUSR1---see the manpage for details. -- Ed ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Aoetools-discuss mailing list Aoetools-discuss@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/aoetools-discuss
