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Date: Thu, 17 Jul 2014 09:26:04 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: Hugh Dickins <hughd@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.cz>,
Minchan Kim <minchan.kim@...il.com>,
Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [patch 3/3] mm: vmscan: clean up struct scan_control
On Mon, Jul 14, 2014 at 12:46:21PM -0700, Hugh Dickins wrote:
> On Mon, 14 Jul 2014, Johannes Weiner wrote:
>
> > Reorder the members by input and output, then turn the individual
> > integers for may_writepage, may_unmap, may_swap, compaction_ready,
> > hibernation_mode into flags that fit into a single integer.
> >
> > Stack delta: +72/-296 -224 old new delta
> > kswapd 104 176 +72
> > try_to_free_pages 80 56 -24
> > try_to_free_mem_cgroup_pages 80 56 -24
> > shrink_all_memory 88 64 -24
> > reclaim_clean_pages_from_list 168 144 -24
> > mem_cgroup_shrink_node_zone 104 80 -24
> > __zone_reclaim 176 152 -24
> > balance_pgdat 152 - -152
> >
> > text data bss dec hex filename
> > 38151 5641 16 43808 ab20 mm/vmscan.o.old
> > 38047 5641 16 43704 aab8 mm/vmscan.o
> >
> > Suggested-by: Mel Gorman <mgorman@...e.de>
> > Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> > ---
> > mm/vmscan.c | 158 ++++++++++++++++++++++++++++++------------------------------
> > 1 file changed, 78 insertions(+), 80 deletions(-)
> >
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index c28b8981e56a..73d8e69ff3eb 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -58,36 +58,28 @@
> > #define CREATE_TRACE_POINTS
> > #include <trace/events/vmscan.h>
> >
> > -struct scan_control {
> > - /* Incremented by the number of inactive pages that were scanned */
> > - unsigned long nr_scanned;
> > -
> > - /* Number of pages freed so far during a call to shrink_zones() */
> > - unsigned long nr_reclaimed;
> > -
> > - /* One of the zones is ready for compaction */
> > - int compaction_ready;
> > +/* Scan control flags */
> > +#define MAY_WRITEPAGE 0x1
> > +#define MAY_UNMAP 0x2
> > +#define MAY_SWAP 0x4
> > +#define MAY_SKIP_CONGESTION 0x8
> > +#define COMPACTION_READY 0x10
> >
> > +struct scan_control {
> > /* How many pages shrink_list() should reclaim */
> > unsigned long nr_to_reclaim;
> >
> > - unsigned long hibernation_mode;
> > -
> > /* This context's GFP mask */
> > gfp_t gfp_mask;
> >
> > - int may_writepage;
> > -
> > - /* Can mapped pages be reclaimed? */
> > - int may_unmap;
> > -
> > - /* Can pages be swapped as part of reclaim? */
> > - int may_swap;
> > -
> > + /* Allocation order */
> > int order;
> >
> > - /* Scan (total_size >> priority) pages at once */
> > - int priority;
> > + /*
> > + * Nodemask of nodes allowed by the caller. If NULL, all nodes
> > + * are scanned.
> > + */
> > + nodemask_t *nodemask;
> >
> > /*
> > * The memory cgroup that hit its limit and as a result is the
> > @@ -95,11 +87,17 @@ struct scan_control {
> > */
> > struct mem_cgroup *target_mem_cgroup;
> >
> > - /*
> > - * Nodemask of nodes allowed by the caller. If NULL, all nodes
> > - * are scanned.
> > - */
> > - nodemask_t *nodemask;
> > + /* Scan (total_size >> priority) pages at once */
> > + int priority;
> > +
> > + /* Scan control flags; see above */
> > + unsigned int flags;
>
> This seems to result in a fair amount of unnecessary churn:
> why not just put may_writepage etc into an unsigned int bitfield,
> then you get the saving without changing all the rest of the code.
Good point, I didn't even think of that. Thanks!
Andrew, could you please replace this patch with the following?
---
>From bbe8c1645c77297a96ecd5d64d659ddcd6984d03 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@...xchg.org>
Date: Mon, 14 Jul 2014 08:51:54 -0400
Subject: [patch] mm: vmscan: clean up struct scan_control
Reorder the members by input and output, then turn the individual
integers for may_writepage, may_unmap, may_swap, compaction_ready,
hibernation_mode into bit fields to save stack space:
+72/-296 -224
kswapd 104 176 +72
try_to_free_pages 80 56 -24
try_to_free_mem_cgroup_pages 80 56 -24
shrink_all_memory 88 64 -24
reclaim_clean_pages_from_list 168 144 -24
mem_cgroup_shrink_node_zone 104 80 -24
__zone_reclaim 176 152 -24
balance_pgdat 152 - -152
Suggested-by: Mel Gorman <mgorman@...e.de>
Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
mm/vmscan.c | 99 ++++++++++++++++++++++++++++---------------------------------
1 file changed, 46 insertions(+), 53 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c28b8981e56a..81dd858b9d17 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -59,35 +59,20 @@
#include <trace/events/vmscan.h>
struct scan_control {
- /* Incremented by the number of inactive pages that were scanned */
- unsigned long nr_scanned;
-
- /* Number of pages freed so far during a call to shrink_zones() */
- unsigned long nr_reclaimed;
-
- /* One of the zones is ready for compaction */
- int compaction_ready;
-
/* How many pages shrink_list() should reclaim */
unsigned long nr_to_reclaim;
- unsigned long hibernation_mode;
-
/* This context's GFP mask */
gfp_t gfp_mask;
- int may_writepage;
-
- /* Can mapped pages be reclaimed? */
- int may_unmap;
-
- /* Can pages be swapped as part of reclaim? */
- int may_swap;
-
+ /* Allocation order */
int order;
- /* Scan (total_size >> priority) pages at once */
- int priority;
+ /*
+ * Nodemask of nodes allowed by the caller. If NULL, all nodes
+ * are scanned.
+ */
+ nodemask_t *nodemask;
/*
* The memory cgroup that hit its limit and as a result is the
@@ -95,11 +80,27 @@ struct scan_control {
*/
struct mem_cgroup *target_mem_cgroup;
- /*
- * Nodemask of nodes allowed by the caller. If NULL, all nodes
- * are scanned.
- */
- nodemask_t *nodemask;
+ /* Scan (total_size >> priority) pages at once */
+ int priority;
+
+ unsigned int may_writepage:1;
+
+ /* Can mapped pages be reclaimed? */
+ unsigned int may_unmap:1;
+
+ /* Can pages be swapped as part of reclaim? */
+ unsigned int may_swap:1;
+
+ unsigned int hibernation_mode:1;
+
+ /* One of the zones is ready for compaction */
+ unsigned int compaction_ready:1;
+
+ /* Incremented by the number of inactive pages that were scanned */
+ unsigned long nr_scanned;
+
+ /* Number of pages freed so far during a call to shrink_zones() */
+ unsigned long nr_reclaimed;
};
#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
@@ -2668,15 +2669,14 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
{
unsigned long nr_reclaimed;
struct scan_control sc = {
+ .nr_to_reclaim = SWAP_CLUSTER_MAX,
.gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
+ .order = order,
+ .nodemask = nodemask,
+ .priority = DEF_PRIORITY,
.may_writepage = !laptop_mode,
- .nr_to_reclaim = SWAP_CLUSTER_MAX,
.may_unmap = 1,
.may_swap = 1,
- .order = order,
- .priority = DEF_PRIORITY,
- .target_mem_cgroup = NULL,
- .nodemask = nodemask,
};
/*
@@ -2706,14 +2706,11 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
unsigned long *nr_scanned)
{
struct scan_control sc = {
- .nr_scanned = 0,
.nr_to_reclaim = SWAP_CLUSTER_MAX,
+ .target_mem_cgroup = memcg,
.may_writepage = !laptop_mode,
.may_unmap = 1,
.may_swap = !noswap,
- .order = 0,
- .priority = 0,
- .target_mem_cgroup = memcg,
};
struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg);
int swappiness = mem_cgroup_swappiness(memcg);
@@ -2748,16 +2745,14 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
unsigned long nr_reclaimed;
int nid;
struct scan_control sc = {
- .may_writepage = !laptop_mode,
- .may_unmap = 1,
- .may_swap = !noswap,
.nr_to_reclaim = SWAP_CLUSTER_MAX,
- .order = 0,
- .priority = DEF_PRIORITY,
- .target_mem_cgroup = memcg,
- .nodemask = NULL, /* we don't care the placement */
.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
+ .target_mem_cgroup = memcg,
+ .priority = DEF_PRIORITY,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = !noswap,
};
/*
@@ -3015,12 +3010,11 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
unsigned long nr_soft_scanned;
struct scan_control sc = {
.gfp_mask = GFP_KERNEL,
+ .order = order,
.priority = DEF_PRIORITY,
+ .may_writepage = !laptop_mode,
.may_unmap = 1,
.may_swap = 1,
- .may_writepage = !laptop_mode,
- .order = order,
- .target_mem_cgroup = NULL,
};
count_vm_event(PAGEOUTRUN);
@@ -3401,14 +3395,13 @@ unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
{
struct reclaim_state reclaim_state;
struct scan_control sc = {
+ .nr_to_reclaim = nr_to_reclaim,
.gfp_mask = GFP_HIGHUSER_MOVABLE,
- .may_swap = 1,
- .may_unmap = 1,
+ .priority = DEF_PRIORITY,
.may_writepage = 1,
- .nr_to_reclaim = nr_to_reclaim,
+ .may_unmap = 1,
+ .may_swap = 1,
.hibernation_mode = 1,
- .order = 0,
- .priority = DEF_PRIORITY,
};
struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
struct task_struct *p = current;
@@ -3588,13 +3581,13 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
struct task_struct *p = current;
struct reclaim_state reclaim_state;
struct scan_control sc = {
- .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
- .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
- .may_swap = 1,
.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
.gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)),
.order = order,
.priority = ZONE_RECLAIM_PRIORITY,
+ .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
+ .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
+ .may_swap = 1,
};
struct shrink_control shrink = {
.gfp_mask = sc.gfp_mask,
--
2.0.0
--
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