From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755089Ab1HYRrh (ORCPT ); Thu, 25 Aug 2011 13:47:37 -0400 Received: from rcsinet15.oracle.com ([148.87.113.117]:62946 "EHLO rcsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755072Ab1HYRrg convert rfc822-to-8bit (ORCPT ); Thu, 25 Aug 2011 13:47:36 -0400 MIME-Version: 1.0 Message-ID: <46a0d040-bae2-4a6b-a896-bc3dadce3cd0@default> Date: Thu, 25 Aug 2011 10:46:52 -0700 (PDT) From: Dan Magenheimer To: KAMEZAWA Hiroyuki Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, jeremy@goop.org, hughd@google.com, ngupta@vflare.org, Konrad Wilk , JBeulich@novell.com, Kurt Hackel , npiggin@kernel.dk, akpm@linux-foundation.org, riel@redhat.com, hannes@cmpxchg.org, matthew@wil.cx, Chris Mason , sjenning@linux.vnet.ibm.com, jackdachef@gmail.com, cyclonusj@gmail.com Subject: RE: Subject: [PATCH V7 3/4] mm: frontswap: add swap hooks and extend try_to_unuse References: <20110823145835.GA23222@ca-server1.us.oracle.com 20110825153347.1e42a607.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20110825153347.1e42a607.kamezawa.hiroyu@jp.fujitsu.com> X-Priority: 3 X-Mailer: Oracle Beehive Extensions for Outlook 2.0.1.4.1.0 (410211) [OL 12.0.6557.5001] Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT X-Source-IP: rtcsinet21.oracle.com [66.248.204.29] X-CT-RefId: str=0001.0A090205.4E568AA1.0185,ss=1,re=0.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: KAMEZAWA Hiroyuki [mailto:kamezawa.hiroyu@jp.fujitsu.com] > Subject: Re: Subject: [PATCH V7 3/4] mm: frontswap: add swap hooks and extend try_to_unuse Thanks again for the great review! I think the only change required for V8 is the addition of a comment in find_next_to_unuse (see below). After reading all of my replies, please let me know if you disagree. Dan > > From: Dan Magenheimer > > > > This third patch of four in the frontswap series adds hooks in the swap > > subsystem and extends try_to_unuse so that frontswap_shrink can do a > > "partial swapoff". Also, declarations for the extern-ified swap variables > > in the first patch are declared. > > > > Note that failed frontswap_map allocation is safe... failure is noted > > by lack of "FS" in the subsequent printk. > > > > [v7: rebase to 3.0-rc3] > > [v7: JBeulich@novell.com: use new static inlines, no-ops if not config'd] > > [v6: rebase to 3.1-rc1] > > [v6: lliubbo@gmail.com: use vzalloc] > > [v5: accidentally posted stale code for v4 that failed to compile :-(] > > [v4: rebase to 2.6.39] > > Signed-off-by: Dan Magenheimer > > Reviewed-by: Konrad Wilk > > Acked-by: Jan Beulich > > Acked-by: Seth Jennings > > Cc: Jeremy Fitzhardinge > > Cc: Hugh Dickins > > Cc: Johannes Weiner > > Cc: Nitin Gupta > > Cc: Matthew Wilcox > > Cc: Chris Mason > > Cc: Rik Riel > > Cc: Andrew Morton > > > > --- linux/mm/swapfile.c 2011-08-08 08:19:26.336684746 -0600 > > +++ frontswap/mm/swapfile.c 2011-08-23 08:21:15.301998803 -0600 > > @@ -32,6 +32,8 @@ > > #include > > #include > > #include > > +#include > > +#include > > > > #include > > #include > > @@ -43,7 +45,7 @@ static bool swap_count_continued(struct > > static void free_swap_count_continuations(struct swap_info_struct *); > > static sector_t map_swap_entry(swp_entry_t, struct block_device**); > > > > -static DEFINE_SPINLOCK(swap_lock); > > +DEFINE_SPINLOCK(swap_lock); > > static unsigned int nr_swapfiles; > > long nr_swap_pages; > > long total_swap_pages; > > @@ -54,9 +56,9 @@ static const char Unused_file[] = "Unuse > > static const char Bad_offset[] = "Bad swap offset entry "; > > static const char Unused_offset[] = "Unused swap offset entry "; > > > > -static struct swap_list_t swap_list = {-1, -1}; > > +struct swap_list_t swap_list = {-1, -1}; > > > > -static struct swap_info_struct *swap_info[MAX_SWAPFILES]; > > +struct swap_info_struct *swap_info[MAX_SWAPFILES]; > > > > static DEFINE_MUTEX(swapon_mutex); > > > > @@ -557,6 +559,7 @@ static unsigned char swap_entry_free(str > > swap_list.next = p->type; > > nr_swap_pages++; > > p->inuse_pages--; > > + frontswap_flush_page(p->type, offset); > > if ((p->flags & SWP_BLKDEV) && > > disk->fops->swap_slot_free_notify) > > disk->fops->swap_slot_free_notify(p->bdev, offset); > > @@ -1022,7 +1025,7 @@ static int unuse_mm(struct mm_struct *mm > > * Recycle to start on reaching the end, returning 0 when empty. > > */ > > static unsigned int find_next_to_unuse(struct swap_info_struct *si, > > - unsigned int prev) > > + unsigned int prev, bool frontswap) > > { > > unsigned int max = si->max; > > unsigned int i = prev; > > @@ -1048,6 +1051,12 @@ static unsigned int find_next_to_unuse(s > > prev = 0; > > i = 1; > > } > > > + if (frontswap) { > > + if (frontswap_test(si, i)) > > + break; > > + else > > + continue; > > + } > > Could you add comment ? If frontswap==true, only scan frontswap ? Yes, thank you, this is a good comment to add. > > @@ -1059,8 +1068,12 @@ static unsigned int find_next_to_unuse(s > > * We completely avoid races by reading each swap page in advance, > > * and then search for the process using it. All the necessary > > * page table adjustments can then be made atomically. > > + * > > + * if the boolean frontswap is true, only unuse pages_to_unuse pages; > > + * pages_to_unuse==0 means all pages; ignored if frontswap is false > > */ > > -static int try_to_unuse(unsigned int type) > > +int try_to_unuse(unsigned int type, bool frontswap, > > + unsigned long pages_to_unuse) > > { > > struct swap_info_struct *si = swap_info[type]; > > struct mm_struct *start_mm; > > @@ -1093,7 +1106,7 @@ static int try_to_unuse(unsigned int typ > > * one pass through swap_map is enough, but not necessarily: > > * there are races when an instance of an entry might be missed. > > */ > > - while ((i = find_next_to_unuse(si, i)) != 0) { > > + while ((i = find_next_to_unuse(si, i, frontswap)) != 0) { > > if (signal_pending(current)) { > > retval = -EINTR; > > break; > > @@ -1260,6 +1273,10 @@ static int try_to_unuse(unsigned int typ > > * interactive performance. > > */ > > cond_resched(); > > + if (frontswap && pages_to_unuse > 0) { > > + if (!--pages_to_unuse) > > + break; > > + } > > } > > Is this a best-effort function and doesn't need to return condition > of pages_to_unuse ? > Caller of try_to_unuse(si, true....) is frontswap_shrink(). Right ? Right. This function is best-effort with frontswap or without frontswap. In a non-frontswap system, a swapoff command may fail because try_to_unuse wasn't able to swap in all pages. The same is true of a "partial swapoff" when frontswap_shrink() is called. Since this behavior didn't change, I didn't add a comment for that. A return condition isn't needed because frontswap_curr_pages can be queried. Thanks! Dan