On Fri, May 18, 2007 at 11:28:24PM -0700, Andrew Morton wrote: > On Thu, 17 May 2007 06:47:53 +0800 Fengguang Wu <wfg@xxxxxxxxxxxxxxxx> wrote: > > > Introduce a new page flag: PG_readahead. > > Is there any way in which we can avoid adding a new page flag? > > We have the advantage that if the kernel very occasionally gets the wrong > result for PageReadahead(page), nothing particularly bad will happen, so we > can do racy things. > > >From a quick peek, it appears that PG_readahead is only ever set against > non-uptodate pages. If true we could perhaps exploit that: say, > PageReadahead(page) == PG_referenced && !PG_uptodate? PG_uptodate will flip to 1 before the reader touches the page :( However, it may be possible to share the same bit with PG_reclaim or PG_booked. Which one would be preferred? - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
