On Sun, 23 Jul 2006, Rik van Riel wrote:
> This patch makes it possible to implement Martin Schwidefsky's
> hypervisor-based fast page reclaiming for architectures without
> millicode - ie. Xen, UML and all other non-s390 architectures.
>
> That could be a big help in heavily loaded virtualized environments.
>
> The fact that it helps prevent the iSCSI memory deadlock is a
> huge bonus too, of course :)
I think there may be a way with less changes to the way the VM functions
to get there:
Add NR_MAPPED_DIRTY and functions to determine easily reclaimable pages.
This patch adds a new counter NR_MAPPED_DIRTY. It tracks the number of
dirty mapped pages. With such a counter we can determine
the number of unmapped clean file backed pages and possibly
use that knowledge to enforce limits in the VM.
Add some new functions:
global_dirty() = Amount of dirty pages in the system as a whole
zone_dirty(zone) = Amount of dirty pages in a specific zone
global_easily_reclaimable() = Amount of clean unmapped pages
(for now. We may want to add other categories later
if we can track more page categories).
zone_easily_reclaimable(zone) = Amount of clean unmapped pages in a zone.
I plan to add later:
global_reclaimable()/zone_reclaimable(zone)
This would be the number of pages that are reclaimable at all regardless
of the effort to be expended:
So this would be
NR_MAPPED + NR_ANON - NR_UNSTABLE_NFS - <mlocked pages> - <pinned pages>
Patch under development. This is just the basis for a discussion.
Other patches could add /proc limits after this one to guarantee
that a certain number of pages is easily reclaimable and so on.
Index: linux-2.6.18-rc1/drivers/base/node.c
===================================================================
--- linux-2.6.18-rc1.orig/drivers/base/node.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/drivers/base/node.c 2006-07-24 10:54:41.667670873 -0700
@@ -58,10 +58,11 @@ static ssize_t node_read_meminfo(struct
"Node %d HighFree: %8lu kB\n"
"Node %d LowTotal: %8lu kB\n"
"Node %d LowFree: %8lu kB\n"
- "Node %d Dirty: %8lu kB\n"
"Node %d Writeback: %8lu kB\n"
"Node %d FilePages: %8lu kB\n"
+ "Node %d Dirty: %8lu kB\n"
"Node %d Mapped: %8lu kB\n"
+ "Node %d DirtyMapped: %8lu kB\n"
"Node %d AnonPages: %8lu kB\n"
"Node %d PageTables: %8lu kB\n"
"Node %d NFS Unstable: %8lu kB\n"
@@ -76,10 +77,11 @@ static ssize_t node_read_meminfo(struct
nid, K(i.freehigh),
nid, K(i.totalram - i.totalhigh),
nid, K(i.freeram - i.freehigh),
- nid, K(node_page_state(nid, NR_FILE_DIRTY)),
nid, K(node_page_state(nid, NR_WRITEBACK)),
nid, K(node_page_state(nid, NR_FILE_PAGES)),
+ nid, K(node_page_state(nid, NR_FILE_DIRTY)),
nid, K(node_page_state(nid, NR_FILE_MAPPED)),
+ nid, K(node_page_state(nid, NR_FILE_MAPPED_DIRTY)),
nid, K(node_page_state(nid, NR_ANON_PAGES)),
nid, K(node_page_state(nid, NR_PAGETABLE)),
nid, K(node_page_state(nid, NR_UNSTABLE_NFS)),
Index: linux-2.6.18-rc1/mm/vmstat.c
===================================================================
--- linux-2.6.18-rc1.orig/mm/vmstat.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/mm/vmstat.c 2006-07-24 10:47:12.662278615 -0700
@@ -389,6 +389,7 @@ static char *vmstat_text[] = {
"nr_slab",
"nr_page_table_pages",
"nr_dirty",
+ "nr_mapped_dirty",
"nr_writeback",
"nr_unstable",
"nr_bounce",
Index: linux-2.6.18-rc1/fs/proc/proc_misc.c
===================================================================
--- linux-2.6.18-rc1.orig/fs/proc/proc_misc.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/fs/proc/proc_misc.c 2006-07-24 10:55:12.832732717 -0700
@@ -167,6 +167,7 @@ static int meminfo_read_proc(char *page,
"Writeback: %8lu kB\n"
"AnonPages: %8lu kB\n"
"Mapped: %8lu kB\n"
+ "DirtyMapped: %8lu kB\n"
"Slab: %8lu kB\n"
"PageTables: %8lu kB\n"
"NFS Unstable: %8lu kB\n"
@@ -193,6 +194,7 @@ static int meminfo_read_proc(char *page,
K(global_page_state(NR_WRITEBACK)),
K(global_page_state(NR_ANON_PAGES)),
K(global_page_state(NR_FILE_MAPPED)),
+ K(global_page_state(NR_FILE_MAPPED_DIRTY)),
K(global_page_state(NR_SLAB)),
K(global_page_state(NR_PAGETABLE)),
K(global_page_state(NR_UNSTABLE_NFS)),
Index: linux-2.6.18-rc1/include/linux/vmstat.h
===================================================================
--- linux-2.6.18-rc1.orig/include/linux/vmstat.h 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/include/linux/vmstat.h 2006-07-24 10:56:44.912966808 -0700
@@ -212,4 +212,61 @@ static inline void refresh_cpu_vm_stats(
static inline void refresh_vm_stats(void) { }
#endif
+static inline void inc_zone_page_dirty(struct page *page)
+{
+ inc_zone_page_state(page, NR_FILE_DIRTY);
+ if (page_mapped(page))
+ inc_zone_page_state(page, NR_FILE_MAPPED_DIRTY);
+}
+
+static inline void dec_zone_page_dirty(struct page *page)
+{
+ dec_zone_page_state(page, NR_FILE_DIRTY);
+ if (page_mapped(page))
+ dec_zone_page_state(page, NR_FILE_MAPPED_DIRTY);
+}
+
+static inline void __inc_zone_page_dirty(struct page *page)
+{
+ __inc_zone_page_state(page, NR_FILE_DIRTY);
+ if (page_mapped(page))
+ __inc_zone_page_state(page, NR_FILE_MAPPED_DIRTY);
+}
+
+static inline void __dec_zone_page_dirty(struct page *page)
+{
+ __dec_zone_page_state(page, NR_FILE_DIRTY);
+ if (page_mapped(page))
+ __dec_zone_page_state(page, NR_FILE_MAPPED_DIRTY);
+}
+
+static inline unsigned long global_dirty(void)
+{
+ return global_page_state(NR_UNSTABLE_NFS) +
+ global_page_state(NR_FILE_DIRTY);
+}
+
+static inline unsigned long zone_dirty(struct zone *z)
+{
+ return zone_page_state(z, NR_UNSTABLE_NFS) +
+ zone_page_state(z, NR_FILE_DIRTY);
+}
+
+static inline unsigned long global_easily_reclaimable(void)
+{
+ return (global_page_state(NR_FILE_PAGES) -
+ global_page_state(NR_FILE_MAPPED))
+ /* Unmapped */ - /* Unmapped dirty */
+ (global_page_state(NR_FILE_DIRTY) -
+ global_page_state(NR_FILE_MAPPED_DIRTY));
+}
+
+static inline unsigned long zone_easily_reclaimable(struct zone *z)
+{
+ return (zone_page_state(z, NR_FILE_PAGES) -
+ zone_page_state(z, NR_FILE_MAPPED))
+ /* Unmapped */ - /* Unmapped dirty */
+ (zone_page_state(z, NR_FILE_DIRTY) -
+ zone_page_state(z, NR_FILE_MAPPED_DIRTY));
+}
#endif /* _LINUX_VMSTAT_H */
Index: linux-2.6.18-rc1/mm/page-writeback.c
===================================================================
--- linux-2.6.18-rc1.orig/mm/page-writeback.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/mm/page-writeback.c 2006-07-24 10:47:12.666184623 -0700
@@ -191,8 +191,7 @@ static void balance_dirty_pages(struct a
};
get_dirty_limits(&background_thresh, &dirty_thresh, mapping);
- nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS);
+ nr_reclaimable = global_dirty();
if (nr_reclaimable + global_page_state(NR_WRITEBACK) <=
dirty_thresh)
break;
@@ -210,8 +209,7 @@ static void balance_dirty_pages(struct a
writeback_inodes(&wbc);
get_dirty_limits(&background_thresh,
&dirty_thresh, mapping);
- nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS);
+ nr_reclaimable = global_dirty();
if (nr_reclaimable +
global_page_state(NR_WRITEBACK)
<= dirty_thresh)
@@ -328,9 +326,7 @@ static void background_writeout(unsigned
long dirty_thresh;
get_dirty_limits(&background_thresh, &dirty_thresh, NULL);
- if (global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) < background_thresh
- && min_pages <= 0)
+ if (global_dirty() < background_thresh && min_pages <= 0)
break;
wbc.encountered_congestion = 0;
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
@@ -354,8 +350,7 @@ static void background_writeout(unsigned
int wakeup_pdflush(long nr_pages)
{
if (nr_pages == 0)
- nr_pages = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS);
+ nr_pages = global_dirty();
return pdflush_operation(background_writeout, nr_pages);
}
@@ -401,8 +396,7 @@ static void wb_kupdate(unsigned long arg
oldest_jif = jiffies - dirty_expire_interval;
start_jif = jiffies;
next_jif = start_jif + dirty_writeback_interval;
- nr_to_write = global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) +
+ nr_to_write = global_dirty() +
(inodes_stat.nr_inodes - inodes_stat.nr_unused);
while (nr_to_write > 0) {
wbc.encountered_congestion = 0;
@@ -624,8 +618,7 @@ int __set_page_dirty_nobuffers(struct pa
if (mapping2) { /* Race with truncate? */
BUG_ON(mapping2 != mapping);
if (mapping_cap_account_dirty(mapping))
- __inc_zone_page_state(page,
- NR_FILE_DIRTY);
+ __inc_zone_page_dirty(page);
radix_tree_tag_set(&mapping->page_tree,
page_index(page), PAGECACHE_TAG_DIRTY);
}
@@ -713,7 +706,7 @@ int test_clear_page_dirty(struct page *p
page_index(page),
PAGECACHE_TAG_DIRTY);
if (mapping_cap_account_dirty(mapping))
- __dec_zone_page_state(page, NR_FILE_DIRTY);
+ __dec_zone_page_dirty(page);
write_unlock_irqrestore(&mapping->tree_lock, flags);
return 1;
}
@@ -745,7 +738,7 @@ int clear_page_dirty_for_io(struct page
if (mapping) {
if (TestClearPageDirty(page)) {
if (mapping_cap_account_dirty(mapping))
- dec_zone_page_state(page, NR_FILE_DIRTY);
+ dec_zone_page_dirty(page);
return 1;
}
return 0;
Index: linux-2.6.18-rc1/include/linux/mmzone.h
===================================================================
--- linux-2.6.18-rc1.orig/include/linux/mmzone.h 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/include/linux/mmzone.h 2006-07-24 10:47:12.667161125 -0700
@@ -54,6 +54,7 @@ enum zone_stat_item {
NR_SLAB, /* Pages used by slab allocator */
NR_PAGETABLE, /* used for pagetables */
NR_FILE_DIRTY,
+ NR_FILE_MAPPED_DIRTY,
NR_WRITEBACK,
NR_UNSTABLE_NFS, /* NFS unstable pages */
NR_BOUNCE,
Index: linux-2.6.18-rc1/mm/vmscan.c
===================================================================
--- linux-2.6.18-rc1.orig/mm/vmscan.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/mm/vmscan.c 2006-07-24 10:47:12.668137627 -0700
@@ -1600,8 +1600,7 @@ int zone_reclaim(struct zone *zone, gfp_
* if less than a specified percentage of the zone is used by
* unmapped file backed pages.
*/
- if (zone_page_state(zone, NR_FILE_PAGES) -
- zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_ratio)
+ if (zone_easily_reclaimable(zone) <= zone->min_unmapped_ratio)
return 0;
/*
Index: linux-2.6.18-rc1/fs/fs-writeback.c
===================================================================
--- linux-2.6.18-rc1.orig/fs/fs-writeback.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/fs/fs-writeback.c 2006-07-24 10:47:12.669114129 -0700
@@ -464,12 +464,9 @@ void sync_inodes_sb(struct super_block *
.range_start = 0,
.range_end = LLONG_MAX,
};
- unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
- unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
- wbc.nr_to_write = nr_dirty + nr_unstable +
- (inodes_stat.nr_inodes - inodes_stat.nr_unused) +
- nr_dirty + nr_unstable;
+ wbc.nr_to_write = 2 * global_dirty() +
+ (inodes_stat.nr_inodes - inodes_stat.nr_unused);
wbc.nr_to_write += wbc.nr_to_write / 2; /* Bit more for luck */
spin_lock(&inode_lock);
sync_sb_inodes(sb, &wbc);
Index: linux-2.6.18-rc1/fs/buffer.c
===================================================================
--- linux-2.6.18-rc1.orig/fs/buffer.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/fs/buffer.c 2006-07-24 10:47:12.671067133 -0700
@@ -851,7 +851,7 @@ int __set_page_dirty_buffers(struct page
write_lock_irq(&mapping->tree_lock);
if (page->mapping) { /* Race with truncate? */
if (mapping_cap_account_dirty(mapping))
- __inc_zone_page_state(page, NR_FILE_DIRTY);
+ __inc_zone_page_dirty(page);
radix_tree_tag_set(&mapping->page_tree,
page_index(page),
PAGECACHE_TAG_DIRTY);
Index: linux-2.6.18-rc1/fs/nfs/write.c
===================================================================
--- linux-2.6.18-rc1.orig/fs/nfs/write.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/fs/nfs/write.c 2006-07-24 10:47:12.673020137 -0700
@@ -496,7 +496,7 @@ nfs_mark_request_dirty(struct nfs_page *
nfs_list_add_request(req, &nfsi->dirty);
nfsi->ndirty++;
spin_unlock(&nfsi->req_lock);
- inc_zone_page_state(req->wb_page, NR_FILE_DIRTY);
+ inc_zone_page_dirty(req->wb_page);
mark_inode_dirty(inode);
}
Index: linux-2.6.18-rc1/fs/nfs/pagelist.c
===================================================================
--- linux-2.6.18-rc1.orig/fs/nfs/pagelist.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/fs/nfs/pagelist.c 2006-07-24 10:47:12.673020137 -0700
@@ -314,7 +314,7 @@ nfs_scan_lock_dirty(struct nfs_inode *nf
req->wb_index, NFS_PAGE_TAG_DIRTY);
nfs_list_remove_request(req);
nfs_list_add_request(req, dst);
- dec_zone_page_state(req->wb_page, NR_FILE_DIRTY);
+ dec_zone_page_dirty(req->wb_page);
res++;
}
}
Index: linux-2.6.18-rc1/mm/rmap.c
===================================================================
--- linux-2.6.18-rc1.orig/mm/rmap.c 2006-07-05 21:09:49.000000000 -0700
+++ linux-2.6.18-rc1/mm/rmap.c 2006-07-24 10:48:49.418980973 -0700
@@ -498,8 +498,11 @@ void page_add_new_anon_rmap(struct page
*/
void page_add_file_rmap(struct page *page)
{
- if (atomic_inc_and_test(&page->_mapcount))
+ if (atomic_inc_and_test(&page->_mapcount)) {
__inc_zone_page_state(page, NR_FILE_MAPPED);
+ if (PageDirty(page))
+ __inc_zone_page_state(page, NR_FILE_MAPPED_DIRTY);
+ }
}
/**
@@ -520,6 +523,7 @@ void page_remove_rmap(struct page *page)
}
#endif
BUG_ON(page_mapcount(page) < 0);
+
/*
* It would be tidy to reset the PageAnon mapping here,
* but that might overwrite a racing page_add_anon_rmap
@@ -529,10 +533,12 @@ void page_remove_rmap(struct page *page)
* Leaving it set also helps swapoff to reinstate ptes
* faster for those pages still in swapcache.
*/
- if (page_test_and_clear_dirty(page))
+ if (page_test_and_clear_dirty(page)) {
+ __dec_zone_page_state(page, NR_FILE_MAPPED_DIRTY);
set_page_dirty(page);
+ }
__dec_zone_page_state(page,
- PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
+ PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
}
}
-
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