From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx119.postini.com [74.125.245.119]) by kanga.kvack.org (Postfix) with SMTP id 359006B0087 for ; Thu, 19 Jul 2012 08:32:44 -0400 (EDT) Date: Thu, 19 Jul 2012 09:32:06 -0300 From: Rafael Aquini Subject: Re: [PATCH v4 1/3] mm: introduce compaction and migration for virtio ballooned pages Message-ID: <20120719123205.GA1752@t510.redhat.com> References: <49f828a9331c9b729fcf77226006921ec5bc52fa.1342485774.git.aquini@redhat.com> <20120718154605.cb0591bc.akpm@linux-foundation.org> <20120718230706.GB2313@t510.redhat.com> <20120718161239.9449e6b5.akpm@linux-foundation.org> <20120719010047.GD2313@t510.redhat.com> <20120718182944.24f59012.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120718182944.24f59012.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" , Rik van Riel , Mel Gorman , Andi Kleen , Konrad Rzeszutek Wilk , Minchan Kim , Rafael Aquini On Wed, Jul 18, 2012 at 06:29:44PM -0700, Andrew Morton wrote: > On Wed, 18 Jul 2012 22:00:48 -0300 Rafael Aquini wrote: > > > > So the function needs a better name - one which communicates that it is > > > a balloon page *for the purposes of processing by the compaction code*. > > > Making the function private to compaction.c would help with that, if > > > feasible. > > > > > > > How about this (adjusted) approach: > > it fails checkpatch ;) > Ugh! it fails due to a lacking whitespace... will fix that right away. > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -1629,8 +1629,7 @@ static inline unsigned int debug_guardpage_minorder(void) > > { return 0; } > > static inline bool page_is_guard(struct page *page) { return false; } > > #endif /* CONFIG_DEBUG_PAGEALLOC */ > > > > -#if (defined(CONFIG_VIRTIO_BALLOON) || \ > > - defined(CONFIG_VIRTIO_BALLOON_MODULE)) && defined(CONFIG_COMPACTION) > > +#if (defined(CONFIG_VIRTIO_BALLOON) ||defined(CONFIG_VIRTIO_BALLOON_MODULE)) > > extern bool putback_balloon_page(struct page *); > > extern struct address_space *balloon_mapping; > > > > @@ -1638,11 +1637,13 @@ static inline bool is_balloon_page(struct page *page) > > { > > return (page->mapping && page->mapping == balloon_mapping); > > } > > +#if defined(CONFIG_COMPACTION) > > +static inline bool balloon_compaction_enabled(void) { return true; } > > #else > > -static inline bool is_balloon_page(struct page *page) { return false; } > > -static inline bool isolate_balloon_page(struct page *page) { return false; } > > -static inline bool putback_balloon_page(struct page *page) { return false; } > > -#endif /* (VIRTIO_BALLOON || VIRTIO_BALLOON_MODULE) && COMPACTION */ > > +static inline bool putback_balloon_page(struct page *page) { return false; } > > +static inline bool balloon_compaction_enabled(void) { return false; } > > +#endif /* CONFIG_COMPACTION */ > > +#endif /* (CONFIG_VIRTIO_BALLOON || CONFIG_VIRTIO_BALLOON_MODULE) */ > > > > #endif /* __KERNEL__ */ > > #endif /* _LINUX_MM_H */ > > diff --git a/mm/migrate.c b/mm/migrate.c > > index 59c7bc5..f5f6a7d 100644 > > --- a/mm/migrate.c > > +++ b/mm/migrate.c > > @@ -78,7 +78,8 @@ void putback_lru_pages(struct list_head *l) > > list_del(&page->lru); > > dec_zone_page_state(page, NR_ISOLATED_ANON + > > page_is_file_cache(page)); > > - if (unlikely(is_balloon_page(page))) > > + if (unlikely(is_balloon_page(page)) && > > + balloon_compaction_enabled()) > > well, that helps readability. But what does is_balloon_page() return > when invoked on a balloon page when CONFIG_COMPACTION=n? False, > methinks. It will (now) return the right thing accordingly to the page->mapping tests. > > I think the code as you previously had it was OK, but the > is_balloon_page() name is misleading. It really wants to be called > is_potentially_compactible_balloon_page() :( Maybe rename it to > compactible_balloon_page()? With all due respect, sir, I don't believe renaming it is the right thing to do. My major supporting reason is since Lumpy Reclaim is already evicted it looks natural CONFIG_COMPACTION=y becoming a permanent feature, thus making that preprocessor test useless and the renamed function signature nonsense, IMHO. That's why I keep respectfully figthing against your argument. Here goes another suggestion, to keep is_balloon_page() name as is. This way I believe all concerns are potentially addressed, as there's no implicit and misleading relationship between is_balloon_page and CONFIG_COMPACTION=y anymore, as well as there are no potential build breakages due to (unexpected) config options. diff --git a/include/linux/mm.h b/include/linux/mm.h index b36d08c..e29ad44 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1629,5 +1629,30 @@ static inline unsigned int debug_guardpage_minorder(void) { return 0; } static inline bool page_is_guard(struct page *page) { return false; } #endif /* CONFIG_DEBUG_PAGEALLOC */ +#if (defined(CONFIG_VIRTIO_BALLOON) || defined(CONFIG_VIRTIO_BALLOON_MODULE)) +extern bool putback_balloon_page(struct page *); +extern struct address_space *balloon_mapping; + +static inline bool is_balloon_page(struct page *page) +{ + return (page->mapping && page->mapping == balloon_mapping); +} + +static inline bool balloon_compaction_enabled(void) +{ +#if defined(CONFIG_COMPACTION) + return true; +#else + return false; +#endif /* CONFIG_COMPACTION */ +} + +#else +static inline bool isolate_balloon_page(struct page *page) { return false; } +static inline bool putback_balloon_page(struct page *page) { return false; } +static inline bool is_balloon_page(struct page *page) { return false; } +static inline bool balloon_compaction_enabled(void) { return false; } +#endif /* (CONFIG_VIRTIO_BALLOON || CONFIG_VIRTIO_BALLOON_MODULE) */ + #endif /* __KERNEL__ */ #endif /* _LINUX_MM_H */ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org