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SubjectRe: Running 2.1.129 at extrem load [patch] (Was: Linux-2.1.129..)
> > Sorry Werner, but this is exactly the place where we need to
> > remove any from of page aging. We can do some kind of aging
> > in the swap cache, page cache and buffer cache, but doing
> > aging here is just prohibitively expensive and needs to be
> > removed.
> >
> > IMHO a better construction be to have a page->fresh flag
> > which would be set on unmapping from swap_out(). Then
> > shrink_mmap() would free pages with page->fresh reset
> > and reset page->fresh if it is set. This way we can
> > free a page at it's second scan so we avoid freeing
> > a page that was just unmapped (and giving each page a
> > bit of a chance to undergo cheap aging).

Comments on the enclosed patch please :-)

* Without the old ageing scheme within try_to_swap_out any
bigger increase of the load causes a temporarily unusable system.

* The `if (buffer_under_min()) break;' within shrink_one_page()
reduces the average system CPU time in comparison to the user
CPU time.

Werner

--------------------------------------------------------------------------
diff -urN linux-2.1.129/include/linux/mm.h linux/include/linux/mm.h
--- linux-2.1.129/include/linux/mm.h Thu Nov 19 20:49:37 1998
+++ linux/include/linux/mm.h Tue Nov 24 00:09:29 1998
@@ -117,7 +117,7 @@
unsigned long offset;
struct page *next_hash;
atomic_t count;
- unsigned int unused;
+ unsigned int lifetime;
unsigned long flags; /* atomic flags, some possibly updated asynchronously */
struct wait_queue *wait;
struct page **pprev_hash;
diff -urN linux-2.1.129/ipc/shm.c linux/ipc/shm.c
--- linux-2.1.129/ipc/shm.c Sun Oct 18 00:52:18 1998
+++ linux/ipc/shm.c Tue Nov 24 12:38:07 1998
@@ -15,6 +15,7 @@
#include <linux/stat.h>
#include <linux/malloc.h>
#include <linux/swap.h>
+#include <linux/swapctl.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
@@ -677,6 +678,11 @@
shm_swp--;
}
shm_rss++;
+
+ /* Increase life time of the page */
+ if (mem_map[MAP_NR(page)].lifetime < 3 && pgcache_under_max())
+ mem_map[MAP_NR(page)].lifetime++;
+
pte = pte_mkdirty(mk_pte(page, PAGE_SHARED));
shp->shm_pages[idx] = pte_val(pte);
} else
diff -urN linux-2.1.129/mm/filemap.c linux/mm/filemap.c
--- linux-2.1.129/mm/filemap.c Thu Nov 19 20:44:18 1998
+++ linux/mm/filemap.c Tue Nov 24 12:25:10 1998
@@ -136,6 +136,8 @@

if (PageLocked(page))
goto next;
+ if (page->lifetime)
+ page->lifetime--;
if ((gfp_mask & __GFP_DMA) && !PageDMA(page))
goto next;
/* First of all, regenerate the page's referenced bit
@@ -167,15 +169,16 @@
case 1:
/* is it a swap-cache or page-cache page? */
if (page->inode) {
- /* Throw swap-cache pages away more aggressively */
- if (PageSwapCache(page)) {
- delete_from_swap_cache(page);
- return 1;
- }
if (test_and_clear_bit(PG_referenced, &page->flags))
break;
if (pgcache_under_min())
break;
+ if (PageSwapCache(page)) {
+ if (page->lifetime && pgcache_under_borrow())
+ break;
+ delete_from_swap_cache(page);
+ return 1;
+ }
remove_inode_page(page);
return 1;
}
@@ -183,7 +186,8 @@
* If it has been referenced recently, don't free it */
if (test_and_clear_bit(PG_referenced, &page->flags))
break;
-
+ if (buffer_under_min())
+ break;
/* is it a buffer cache page? */
if (bh && try_to_free_buffer(bh, &bh, 6))
return 1;
diff -urN linux-2.1.129/mm/page_alloc.c linux/mm/page_alloc.c
--- linux-2.1.129/mm/page_alloc.c Thu Nov 19 20:44:18 1998
+++ linux/mm/page_alloc.c Tue Nov 24 12:37:30 1998
@@ -231,11 +231,13 @@
map += size; \
} \
atomic_set(&map->count, 1); \
+ map->lifetime = 0; \
} while (0)

unsigned long __get_free_pages(int gfp_mask, unsigned long order)
{
unsigned long flags;
+ int loop = 0;

if (order >= NR_MEM_LISTS)
goto nopage;
@@ -262,6 +264,7 @@
goto nopage;
}
}
+repeat:
spin_lock_irqsave(&page_alloc_lock, flags);
RMQUEUE(order, (gfp_mask & GFP_DMA));
spin_unlock_irqrestore(&page_alloc_lock, flags);
@@ -274,6 +277,8 @@
if (gfp_mask & __GFP_WAIT) {
current->policy |= SCHED_YIELD;
schedule();
+ if (!loop++ && nr_free_pages > freepages.low)
+ goto repeat;
}

nopage:
@@ -399,6 +404,10 @@
vma->vm_mm->rss++;
tsk->min_flt++;
swap_free(entry);
+
+ /* Increase life time of the page */
+ if (page_map->lifetime < 3 && pgcache_under_max())
+ page_map->lifetime++;

if (!write_access || is_page_shared(page_map)) {
set_pte(page_table, mk_pte(page, vma->vm_page_prot));
diff -urN linux-2.1.129/mm/swap.c linux/mm/swap.c
--- linux-2.1.129/mm/swap.c Wed Sep 9 17:56:59 1998
+++ linux/mm/swap.c Tue Nov 24 13:08:19 1998
@@ -76,7 +76,7 @@

buffer_mem_t page_cache = {
5, /* minimum percent page cache */
- 30, /* borrow percent page cache */
+ 25, /* borrow percent page cache */
75 /* maximum */
};

diff -urN linux-2.1.129/mm/vmscan.c linux/mm/vmscan.c
--- linux-2.1.129/mm/vmscan.c Thu Nov 19 20:44:18 1998
+++ linux/mm/vmscan.c Tue Nov 24 00:06:20 1998
@@ -561,6 +561,7 @@
int try_to_free_pages(unsigned int gfp_mask, int count)
{
int retval = 1;
+ int is_dma = (gfp_mask & __GFP_DMA);

lock_kernel();
if (!(current->flags & PF_MEMALLOC)) {
@@ -568,6 +569,8 @@
do {
retval = do_try_to_free_page(gfp_mask);
if (!retval)
+ break;
+ if (!is_dma && nr_free_pages > freepages.high + SWAP_CLUSTER_MAX)
break;
count--;
} while (count > 0);
-
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