Messages in this thread | | | Subject | Re: [PATCH] fbdefio: add set_page_dirty handler to deferred IO FB | From | Markus Armbruster <> | Date | Wed, 20 Aug 2008 08:27:33 -0400 |
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"Jaya Kumar" <jayakumar.lkml@gmail.com> writes:
> On Tue, Aug 19, 2008 at 2:38 AM, Andrew Morton > <akpm@linux-foundation.org> wrote: >> On Tue, 19 Aug 2008 07:02:45 +0100 Ian Campbell <ijc@hellion.org.uk> wrote: >> >>> +static int fb_deferred_io_set_page_dirty(struct page *page) >>> +{ >>> + if (!PageDirty(page)) >>> + SetPageDirty(page); >>> + return 0; >>> +} >> >> <searches, finds the thread. "kernel BUG at lib/radix-tree.c:473!"> >> >> Is there actually any benefit in setting these pages dirty? Or should >> this be an empty function? I see claims in the above thread that this >> driver uses PG_dirty for optimising writeback but I can't immediately >> locate any code which actually does that. > > Hi Andrew, > > I hope I have understood your question. You are right that PG_dirty > isn't used directly in defio. The defio portion does use each > page_mkwrite callback to build a list of the pages of the framebuffer > that were written to and then passes that list to pvfb (in this case). > pvfb then optimizes writeback by interpreting that list according to > its framebuffer and sending it to its actual destination. I think > Markus's code in xenfb_deferred_io() and xenfb_send* is doing the > latter.
Exactly. xenfb_deferred_io() is the callback that receives the list of pages that have been dirtied from fb_deferred_io_work(). It computes a rectangle covering all these pages, and passes it to xenfb_refresh(). Which takes care of sending it to the backend.
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