Messages in this thread Patch in this message | | | Date | Fri, 27 Mar 2009 15:30:35 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] vmscan: memcg needs may_swap (Re: [patch] vmscan: rename sc.may_swap to may_unmap) |
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On Fri, 27 Mar 2009 15:19:26 +0900 Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> Added > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > Cc: Balbir Singh <balbir@in.ibm.com> > > I'm sorry for replying to a very old mail. > > > @@ -1713,7 +1713,7 @@ unsigned long try_to_free_mem_cgroup_pag > > { > > struct scan_control sc = { > > .may_writepage = !laptop_mode, > > - .may_swap = 1, > > + .may_unmap = 1, > > .swap_cluster_max = SWAP_CLUSTER_MAX, > > .swappiness = swappiness, > > .order = 0, > > @@ -1723,7 +1723,7 @@ unsigned long try_to_free_mem_cgroup_pag > > struct zonelist *zonelist; > > > > if (noswap) > > - sc.may_swap = 0; > > + sc.may_unmap = 0; > > > > sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | > > (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); > IIUC, memcg had used may_swap as a flag for "we need to use swap?" as the name indicate. > > Because, when mem+swap hits the limit, trying to swapout pages is meaningless > as it doesn't change mem+swap usage. > Good catch...sigh, I missed this disussion.
> What do you think of this patch? > === > From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> > > vmscan-rename-scmay_swap-to-may_unmap.patch removed may_swap flag, > but memcg had used it as a flag for "we need to use swap?", as the > name indicate. > > And in current implementation, memcg cannot reclaim mapped file caches > when mem+swap hits the limit. > When mem+swap hits the limit, swap-out anonymous page doesn't reduce the amount of usage of mem+swap, so, swap-out should be avoided.
> re-introduce may_swap flag and handle it at shrink_page_list. > > This patch doesn't influence any scan_control users other than memcg. >
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Seems good, Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
But hum....Maybe this lru scan work in the same way as the case of !total_swap_pages. (means don't scan anon LRU.) revisit this later.
-Kame
> --- > mm/vmscan.c | 15 ++++++++++++++- > 1 files changed, 14 insertions(+), 1 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index c815653..86118d9 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -64,6 +64,9 @@ struct scan_control { > /* Can mapped pages be reclaimed? */ > int may_unmap; > > + /* Can pages be swapped as part of reclaim? */ > + int may_swap; > + > /* This context's SWAP_CLUSTER_MAX. If freeing memory for > * suspend, we effectively ignore SWAP_CLUSTER_MAX. > * In this context, it doesn't matter that we scan the > @@ -616,6 +619,11 @@ static unsigned long shrink_page_list(struct list_head *page_list, > if (!sc->may_unmap && page_mapped(page)) > goto keep_locked; > > + if (!sc->may_swap && PageSwapBacked(page) > + /* SwapCache uses 'swap' already */ > + && !PageSwapCache(page)) > + goto keep_locked; > + > /* Double the slab pressure for mapped and swapcache pages */ > if (page_mapped(page) || PageSwapCache(page)) > sc->nr_scanned++; > @@ -1696,6 +1704,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, > .may_writepage = !laptop_mode, > .swap_cluster_max = SWAP_CLUSTER_MAX, > .may_unmap = 1, > + .may_swap = 1, > .swappiness = vm_swappiness, > .order = order, > .mem_cgroup = NULL, > @@ -1715,6 +1724,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, > struct scan_control sc = { > .may_writepage = !laptop_mode, > .may_unmap = 1, > + .may_swap = 1, > .swap_cluster_max = SWAP_CLUSTER_MAX, > .swappiness = swappiness, > .order = 0, > @@ -1724,7 +1734,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, > struct zonelist *zonelist; > > if (noswap) > - sc.may_unmap = 0; > + sc.may_swap = 0; > > sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | > (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); > @@ -1764,6 +1774,7 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order) > struct scan_control sc = { > .gfp_mask = GFP_KERNEL, > .may_unmap = 1, > + .may_swap = 1, > .swap_cluster_max = SWAP_CLUSTER_MAX, > .swappiness = vm_swappiness, > .order = order, > @@ -2110,6 +2121,7 @@ unsigned long shrink_all_memory(unsigned long nr_pages) > struct scan_control sc = { > .gfp_mask = GFP_KERNEL, > .may_unmap = 0, > + .may_swap = 1, > .may_writepage = 1, > .isolate_pages = isolate_pages_global, > }; > @@ -2292,6 +2304,7 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) > struct scan_control sc = { > .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), > .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), > + .may_swap = 1, > .swap_cluster_max = max_t(unsigned long, nr_pages, > SWAP_CLUSTER_MAX), > .gfp_mask = gfp_mask, >
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