On Wed, 13 Dec 2006 00:45:50 -0800 Suleiman Souhlal <[EMAIL PROTECTED]> wrote:
> [EMAIL PROTECTED] wrote: > > From: Andrew Morton <[EMAIL PROTECTED]> > > > > Accounting writes is fairly simple: whenever a process flips a page from > > clean > > to dirty, we accuse it of having caused a write to underlying storage of > > PAGE_CACHE_SIZE bytes. > > On architectures where dirtying a page doesn't cause a page fault (like > i386), couldn't you end up billing the wrong process (in fact, I think that > even on other archituctures set_page_dirty() doesn't get called immediately > in the page fault handler)? Yes, that would be a problem in 2.6.18 and earlier. In 2.6.19 and later, we do take a fault when transitioning a page from pte-clean to pte-dirty. That was done to get the dirty-page accounting right - to avoid the all-of-memory-is-dirty-but-the-kernel-doesn't-know-it problem. > AFAICS, set_page_dirty() is mostly called when trying to unmap a page when > trying to shrink LRU lists, and there is no guarantee that this happens under > the process that dirtied it (in fact, the set_page_dirty() is often done by > kswapd). hm, that code is still there in zap_pte_range(). If all is well, that set_page_dirty() call should never return true. Peter did, you ever test for that? (Well, it might return true in rare races, because zap_pte_range() doesn't lock the pages) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
