Re: [PATCH/RFC 0/4] VM: Manual and Automatic page cache reclaim

Martin Hicks
2005-05-12T18:57:05Z

On Thu, May 12, 2005 at 02:53:02PM -0400, Martin Hicks wrote:
>
> So, I did this as an exercise. A few things came up:

and this time here's the patch. Its against something like
2.6.12-rc3-mm3

mh

Index: linux-2.6.12-rc3/arch/ia64/kernel/entry.S
===================================================================
--- linux-2.6.12-rc3.orig/arch/ia64/kernel/entry.S 2005-05-12 10:07:56.000000000 -0700
+++ linux-2.6.12-rc3/arch/ia64/kernel/entry.S 2005-05-12 10:08:14.000000000 -0700
@@ -1573,7 +1573,7 @@ sys_call_table:
data8 sys_keyctl
data8 sys_ni_syscall
data8 sys_ni_syscall // 1275
- data8 sys_ni_syscall
+ data8 sys_set_zone_reclaim
data8 sys_ni_syscall
data8 sys_ni_syscall
data8 sys_ni_syscall
Index: linux-2.6.12-rc3/include/linux/mmzone.h
===================================================================
--- linux-2.6.12-rc3.orig/include/linux/mmzone.h 2005-05-12 10:07:56.000000000 -0700
+++ linux-2.6.12-rc3/include/linux/mmzone.h 2005-05-12 10:12:20.000000000 -0700
@@ -163,6 +163,12 @@ struct zone {
int temp_priority;
int prev_priority;

+ /*
+ * Does the zone try to reclaim before giving allowing the allocator
+ * to try the next zone?
+ */
+ int reclaim_pages;
+ int reclaim_pages_failed;

ZONE_PADDING(_pad2_)
/* Rarely used or read-mostly fields */
Index: linux-2.6.12-rc3/include/linux/swap.h
===================================================================
--- linux-2.6.12-rc3.orig/include/linux/swap.h 2005-05-12 10:07:56.000000000 -0700
+++ linux-2.6.12-rc3/include/linux/swap.h 2005-05-12 10:08:14.000000000 -0700
@@ -173,6 +173,7 @@ extern void swap_setup(void);

/* linux/mm/vmscan.c */
extern int try_to_free_pages(struct zone **, unsigned int, unsigned int);
+extern int zone_reclaim(struct zone *, unsigned int, unsigned int);
extern int shrink_all_memory(int);
extern int vm_swappiness;

Index: linux-2.6.12-rc3/mm/page_alloc.c
===================================================================
--- linux-2.6.12-rc3.orig/mm/page_alloc.c 2005-05-12 10:07:56.000000000 -0700
+++ linux-2.6.12-rc3/mm/page_alloc.c 2005-05-12 10:13:30.000000000 -0700
@@ -349,6 +349,7 @@ free_pages_bulk(struct zone *zone, int c

spin_lock_irqsave(&zone->lock, flags);
zone->all_unreclaimable = 0;
+ zone->reclaim_pages_failed = 0;
zone->pages_scanned = 0;
while (!list_empty(list) && count--) {
page = list_entry(list->prev, struct page, lru);
@@ -761,14 +762,29 @@ __alloc_pages(unsigned int __nocast gfp_
restart:
/* Go through the zonelist once, looking for a zone with enough free */
for (i = 0; (z = zones[i]) != NULL; i++) {
-
- if (!zone_watermark_ok(z, order, z->pages_low,
- classzone_idx, 0, 0))
- continue;
+ int do_reclaim = z->reclaim_pages;

if (!cpuset_zone_allowed(z))
continue;

+ /*
+ * If the zone is to attempt early page reclaim hen this loop
+ * will try to reclaim pages and check the watermark a second
+ * time before giving up and falling back to the next zone.
+ */
+ zone_reclaim_retry:
+ if (!zone_watermark_ok(z, order, z->pages_low,
+ classzone_idx, 0, 0)) {
+ if (!do_reclaim)
+ continue;
+ else {
+ zone_reclaim(z, gfp_mask, order);
+ /* Only try reclaim once */
+ do_reclaim = 0;
+ goto zone_reclaim_retry;
+ }
+ }
+
page = buffered_rmqueue(z, order, gfp_mask);
if (page)
goto got_pg;
Index: linux-2.6.12-rc3/mm/vmscan.c
===================================================================
--- linux-2.6.12-rc3.orig/mm/vmscan.c 2005-05-12 10:07:56.000000000 -0700
+++ linux-2.6.12-rc3/mm/vmscan.c 2005-05-12 10:11:31.000000000 -0700
@@ -73,6 +73,7 @@ struct scan_control {
unsigned int gfp_mask;

int may_writepage;
+ int may_swap;

/* This context's SWAP_CLUSTER_MAX. If freeing memory for
* suspend, we effectively ignore SWAP_CLUSTER_MAX.
@@ -414,7 +415,7 @@ static int shrink_list(struct list_head
* Anonymous process memory has backing store?
* Try to allocate it some swap space here.
*/
- if (PageAnon(page) && !PageSwapCache(page)) {
+ if (PageAnon(page) && !PageSwapCache(page) && sc->may_swap) {
void *cookie = page->mapping;
pgoff_t index = page->index;

@@ -944,6 +945,7 @@ int try_to_free_pages(struct zone **zone

sc.gfp_mask = gfp_mask;
sc.may_writepage = 0;
+ sc.may_swap = 1;

inc_page_state(allocstall);

@@ -1044,6 +1046,7 @@ loop_again:
total_reclaimed = 0;
sc.gfp_mask = GFP_KERNEL;
sc.may_writepage = 0;
+ sc.may_swap = 1;
sc.nr_mapped = read_page_state(nr_mapped);

inc_page_state(pageoutrun);
@@ -1335,3 +1338,69 @@ static int __init kswapd_init(void)
}

module_init(kswapd_init)
+
+
+/*
+ * Try to free up some pages from this zone through reclaim.
+ */
+int zone_reclaim(struct zone *zone, unsigned int gfp_mask, unsigned int order)
+{
+ struct scan_control sc;
+ int nr_pages = 1 << order;
+ int priority;
+ int total_reclaimed = 0;
+
+ /* The reclaim may sleep, so don't do it if sleep isn't allowed */
+ if (!(gfp_mask & __GFP_WAIT))
+ return 0;
+ if (zone->reclaim_pages_failed)
+ return 0;
+
+ sc.gfp_mask = gfp_mask;
+ sc.may_writepage = 0;
+ sc.may_swap = 0;
+ sc.nr_mapped = read_page_state(nr_mapped);
+ sc.nr_scanned = 0;
+ sc.nr_reclaimed = 0;
+ sc.priority = 0; /* scan at the highest priority */
+
+ if (nr_pages > SWAP_CLUSTER_MAX)
+ sc.swap_cluster_max = nr_pages;
+ else
+ sc.swap_cluster_max = SWAP_CLUSTER_MAX;
+
+ shrink_zone(zone, &sc);
+
+ if (sc.nr_reclaimed < nr_pages)
+ zone->reclaim_pages_failed = 1;
+
+ return total_reclaimed;
+}
+
+asmlinkage long sys_set_zone_reclaim(unsigned int node, unsigned int zone,
+ unsigned int state)
+{
+ struct zone *z;
+ int i;
+
+ if (node >= MAX_NUMNODES || !node_online(node))
+ return -EINVAL;
+
+ /* This will break if we ever add more zones */
+ if (!(zone & (1<<ZONE_DMA|1<<ZONE_NORMAL|1<<ZONE_HIGHMEM)))
+ return -EINVAL;
+
+ for (i = 0; i < MAX_NR_ZONES; i++) {
+ if (!(zone & 1<<i))
+ continue;
+
+ z = &NODE_DATA(node)->node_zones[i];
+
+ if (state)
+ z->reclaim_pages = 1;
+ else
+ z->reclaim_pages = 0;
+ }
+
+ return 0;
+}
Index: linux-2.6.12-rc3/kernel/sys_ni.c
===================================================================
--- linux-2.6.12-rc3.orig/kernel/sys_ni.c 2005-05-12 10:07:56.000000000 -0700
+++ linux-2.6.12-rc3/kernel/sys_ni.c 2005-05-12 10:09:18.000000000 -0700
@@ -77,6 +77,7 @@ cond_syscall(sys_request_key);
cond_syscall(sys_keyctl);
cond_syscall(compat_sys_keyctl);
cond_syscall(compat_sys_socketcall);
+cond_syscall(sys_set_zone_reclaim);

/* arch-specific weak syscall entries */
cond_syscall(sys_pciconfig_read);