> From: KAMEZAWA Hiroyuki [mailto:kamezawa.hiroyu@xxxxxxxxxxxxxx] > 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 <dan.magenheimer@xxxxxxxxxx> > > > > 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@xxxxxxxxxx: use new static inlines, no-ops if not config'd] > > [v6: rebase to 3.1-rc1] > > [v6: lliubbo@xxxxxxxxx: use vzalloc] > > [v5: accidentally posted stale code for v4 that failed to compile :-(] > > [v4: rebase to 2.6.39] > > Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> > > Reviewed-by: Konrad Wilk <konrad.wilk@xxxxxxxxxx> > > Acked-by: Jan Beulich <JBeulich@xxxxxxxxxx> > > Acked-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx> > > Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx> > > Cc: Hugh Dickins <hughd@xxxxxxxxxx> > > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > > Cc: Nitin Gupta <ngupta@xxxxxxxxxx> > > Cc: Matthew Wilcox <matthew@xxxxxx> > > Cc: Chris Mason <chris.mason@xxxxxxxxxx> > > Cc: Rik Riel <riel@xxxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > > > --- 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 <linux/memcontrol.h> > > #include <linux/poll.h> > > #include <linux/oom.h> > > +#include <linux/frontswap.h> > > +#include <linux/swapfile.h> > > > > #include <asm/pgtable.h> > > #include <asm/tlbflush.h> > > @@ -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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href