On Mon, Jun 03, 2013 at 07:53:01AM -0700, Dave Hansen wrote: > On 06/02/2013 10:40 PM, Minchan Kim wrote: > >> > diff -puN mm/vmscan.c~__delete_from_swap_cache-dont-clear-page-private > >> > mm/vmscan.c > >> > --- > >> > linux.git/mm/vmscan.c~__delete_from_swap_cache-dont-clear-page-private > >> > 2013-05-30 16:07:50.632079492 -0700 > >> > +++ linux.git-davehans/mm/vmscan.c 2013-05-30 16:07:50.637079712 > >> > -0700 > >> > @@ -494,6 +494,8 @@ static int __remove_mapping(struct addre > >> > __delete_from_swap_cache(page); > >> > spin_unlock_irq(&mapping->tree_lock); > >> > swapcache_free(swap, page); > >> > + set_page_private(page, 0); > >> > + ClearPageSwapCache(page); > > It it worth to support non-atomic version of ClearPageSwapCache? > > Just for this, probably not. > > It does look like a site where it would be theoretically safe to use > non-atomic flag operations since the page is on a one-way trip to the > allocator at this point and the __clear_page_locked() now happens _just_ > after this code.
True. > > But, personally, I'm happy to leave it as-is. The atomic vs. non-atomic > flags look to me like a micro-optimization that we should use when we > _know_ there will be some tangible benefit. Otherwise, they're just > something extra for developers to trip over and cause very subtle bugs. I just asked it because when I read the description of patchset, I felt you were very sensitive to the atomic operation on many CPU system with several sockets. Anyway, if you don't want it, I don't mind it, either. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
