Re: More info: 2.1.108 page cache performance on low memory

["Dr. Werner Fink" <werner@suse.de>]

On Thu, Jul 23, 1998 at 12:59:38PM +0200, Zlatko Calusic wrote:
> 
> I tried the other way, to age page cache harder, and it looks like it
> works very well. Patch is simple, so simple that I can't understand
> nobody suggested (something like) it yet.
> 
> 
> --- filemap.c.virgin   Tue Jul 21 18:41:30 1998
> +++ filemap.c   Thu Jul 23 12:14:43 1998
> @@ -171,6 +171,11 @@
>                                 touch_page(page);
>                                 break;
>                         }
> +                       /* Age named pages aggresively, so page cache
> +                        * doesn't grow too fast.    -zcalusic
> +                        */
> +                       age_page(page);
> +                       age_page(page);
>                         age_page(page);
>                         if (page->age)
>                                 break;
> 

I've something similar ... cut&paste (no tabs) ... which would only do
less graduated ageing on small systems.

------------------------------------------------------------------------------- 
diff -urN linux-2.1.110/include/linux/swapctl.h linux/include/linux/swapctl.h
--- linux-2.1.110/include/linux/swapctl.h       Tue Jul 21 02:32:01 1998
+++ linux/include/linux/swapctl.h       Wed Jul 22 18:04:28 1998
@@ -94,12 +94,26 @@
                return n;
 }
 
+extern int pgcache_max_age;
+extern void do_pgcache_max_age(void);
+
 static inline void touch_page(struct page *page)
 {
-       if (page->age < (MAX_PAGE_AGE - PAGE_ADVANCE))
+       int max_age = MAX_PAGE_AGE;
+
+       if (atomic_read(&page->count) == 1) {
+               static int save_max_age = 0;
+               if (save_max_age != max_age) {
+                       save_max_age = max_age;
+                       do_pgcache_max_age();
+               }
+               max_age = pgcache_max_age;
+       }
+
+       if (page->age < (max_age - PAGE_ADVANCE))
                page->age += PAGE_ADVANCE;
        else
-               page->age = MAX_PAGE_AGE;
+               page->age = max_age;
 }
 
 static inline void age_page(struct page *page)
diff -urN linux-2.1.110/include/linux/swapctl.h linux/include/linux/swapctl.h
--- linux-2.1.110/include/linux/swapctl.h       Tue Jul 21 02:32:01 1998
+++ linux/include/linux/swapctl.h       Wed Jul 22 18:04:28 1998
@@ -94,12 +94,26 @@
                return n;
 }
 
+extern int pgcache_max_age;
+extern void do_pgcache_max_age(void);
+
 static inline void touch_page(struct page *page)
 {
-       if (page->age < (MAX_PAGE_AGE - PAGE_ADVANCE))
+       int max_age = MAX_PAGE_AGE;
+
+       if (atomic_read(&page->count) == 1) {
+               static int save_max_age = 0;
+               if (save_max_age != max_age) {
+                       save_max_age = max_age;
+                       do_pgcache_max_age();
+               }
+               max_age = pgcache_max_age;
+       }
+
+       if (page->age < (max_age - PAGE_ADVANCE))
                page->age += PAGE_ADVANCE;
        else
-               page->age = MAX_PAGE_AGE;
+               page->age = max_age;
 }
 
 static inline void age_page(struct page *page)
------------------------------------------------------------------------------- 



        Werner
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