Use the read-ahead code to provide hints to page reclaim.
This patch has the potential to solve the streaming-IO trashes my
desktop problem.
It tries to aggressively reclaim pages that were loaded in a strong
sequential pattern and have been consumed. Thereby limiting the damage
to the current resident set.
I'm posting this in the hope that people will test this in a variety of
workloads and report back (success or regression). It seems to work
reasonably well on my desktop for things that sequentially consume large
files: burning dvds, md5sum dvds, cat dvds > /dev/null
Signed-off-by: Peter Zijlstra <[email protected]>
---
include/linux/swap.h | 1 +
mm/readahead.c | 38 +++++++++++++++++++++++++++++++++++++-
mm/swap.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 89 insertions(+), 1 deletion(-)
Index: linux-2.6/mm/swap.c
===================================================================
--- linux-2.6.orig/mm/swap.c
+++ linux-2.6/mm/swap.c
@@ -31,6 +31,7 @@
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <linux/init.h>
+#include <linux/rmap.h>
/* How many pages do we try to swap or page in/out together? */
int page_cluster;
@@ -178,6 +179,7 @@ EXPORT_SYMBOL(mark_page_accessed);
static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
static DEFINE_PER_CPU(struct pagevec, lru_add_tail_pvecs) = { 0, };
+static DEFINE_PER_CPU(struct pagevec, lru_demote_pvecs) = { 0, };
void fastcall lru_cache_add(struct page *page)
{
@@ -224,6 +226,37 @@ static void __pagevec_lru_add_tail(struc
pagevec_reinit(pvec);
}
+static void __pagevec_lru_demote(struct pagevec *pvec)
+{
+ int i;
+ struct zone *zone = NULL;
+
+ for (i = 0; i < pagevec_count(pvec); i++) {
+ struct page *page = pvec->pages[i];
+ struct zone *pagezone = page_zone(page);
+
+ if (pagezone != zone) {
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ zone = pagezone;
+ spin_lock_irq(&zone->lru_lock);
+ }
+ if (PageLRU(page)) {
+ page_referenced(page, 0);
+ if (PageActive(page)) {
+ ClearPageActive(page);
+ __dec_zone_state(zone, NR_ACTIVE);
+ __inc_zone_state(zone, NR_INACTIVE);
+ }
+ list_move_tail(&page->lru, &zone->inactive_list);
+ }
+ }
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ release_pages(pvec->pages, pvec->nr, pvec->cold);
+ pagevec_reinit(pvec);
+}
+
static void __lru_add_drain(int cpu)
{
struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
@@ -237,6 +270,9 @@ static void __lru_add_drain(int cpu)
pvec = &per_cpu(lru_add_tail_pvecs, cpu);
if (pagevec_count(pvec))
__pagevec_lru_add_tail(pvec);
+ pvec = &per_cpu(lru_demote_pvecs, cpu);
+ if (pagevec_count(pvec))
+ __pagevec_lru_demote(pvec);
}
void lru_add_drain(void)
@@ -448,6 +484,21 @@ void fastcall lru_cache_add_tail(struct
}
/*
+ * Function used to forcefully demote a page to the tail of the inactive
+ * list.
+ */
+void fastcall lru_demote(struct page *page)
+{
+ if (likely(get_page_unless_zero(page))) {
+ struct pagevec *pvec = &get_cpu_var(lru_demote_pvecs);
+
+ if (!pagevec_add(pvec, page))
+ __pagevec_lru_demote(pvec);
+ put_cpu_var(lru_demote_pvecs);
+ }
+}
+
+/*
* Try to drop buffers from the pages in a pagevec
*/
void pagevec_strip(struct pagevec *pvec)
Index: linux-2.6/include/linux/swap.h
===================================================================
--- linux-2.6.orig/include/linux/swap.h
+++ linux-2.6/include/linux/swap.h
@@ -181,6 +181,7 @@ extern unsigned int nr_free_pagecache_pa
extern void FASTCALL(lru_cache_add(struct page *));
extern void FASTCALL(lru_cache_add_active(struct page *));
extern void FASTCALL(lru_cache_add_tail(struct page *));
+extern void FASTCALL(lru_demote(struct page *));
extern void FASTCALL(activate_page(struct page *));
extern void FASTCALL(mark_page_accessed(struct page *));
extern void lru_add_drain(void);
Index: linux-2.6/mm/readahead.c
===================================================================
--- linux-2.6.orig/mm/readahead.c
+++ linux-2.6/mm/readahead.c
@@ -15,6 +15,7 @@
#include <linux/backing-dev.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/pagevec.h>
+#include <linux/swap.h>
void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
{
@@ -441,13 +442,18 @@ EXPORT_SYMBOL_GPL(page_cache_sync_readah
* page_cache_async_ondemand() should be called when a page is used which
* has the PG_readahead flag: this is a marker to suggest that the application
* has used up enough of the readahead window that we should start pulling in
- * more pages. */
+ * more pages.
+ */
void
page_cache_async_readahead(struct address_space *mapping,
struct file_ra_state *ra, struct file *filp,
struct page *page, pgoff_t offset,
unsigned long req_size)
{
+ unsigned long demote_idx = offset - min(offset, ra->size);
+ struct page *pages[16];
+ unsigned nr_pages, i;
+
/* no read-ahead */
if (!ra->ra_pages)
return;
@@ -466,6 +472,36 @@ page_cache_async_readahead(struct addres
if (bdi_read_congested(mapping->backing_dev_info))
return;
+ /*
+ * Read-ahead use once: when the ra window is maximal this is a good
+ * hint that there is sequential IO, which implies that the pages that
+ * have been used thus far can be reclaimed
+ */
+ if (ra->size == ra->ra_pages) do {
+ nr_pages = find_get_pages(mapping,
+ demote_idx, ARRAY_SIZE(pages), pages);
+
+ for (i = 0; i < nr_pages; i++) {
+ page = pages[i];
+ demote_idx = page_index(page);
+
+ /*
+ * The page is active. This means there are other
+ * users. We should not take away somebody else's
+ * pages, so do not drop behind beyond this point.
+ */
+ if (demote_idx < offset && !PageActive(page)) {
+ lru_demote(page);
+ } else {
+ demote_idx = offset;
+ break;
+ }
+ }
+ demote_idx++;
+
+ release_pages(pages, nr_pages, 0);
+ } while (demote_idx < offset);
+
/* do read-ahead */
ondemand_readahead(mapping, ra, filp, true, offset, req_size);
}
-
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