From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx106.postini.com [74.125.245.106]) by kanga.kvack.org (Postfix) with SMTP id 966B16B0068 for ; Wed, 18 Jul 2012 21:25:25 -0400 (EDT) Date: Wed, 18 Jul 2012 18:29:44 -0700 From: Andrew Morton Subject: Re: [PATCH v4 1/3] mm: introduce compaction and migration for virtio ballooned pages Message-Id: <20120718182944.24f59012.akpm@linux-foundation.org> In-Reply-To: <20120719010047.GD2313@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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Rafael Aquini 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, 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 ;) > --- 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. 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()? -- 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