Help with shared memory usage

[Wandenberg Peixoto]

Hello!

Thanks for your help. I hope that the patch be OK now.
I don't know if the function and variable names are on nginx pattern.
Feel free to change the patch.
If you have any other point before accept it, will be a pleasure to fix it.

--- src/core/ngx_slab.c    2013-05-06 07:27:10.000000000 -0300
+++ src/core/ngx_slab.c    2013-07-31 00:21:08.043034442 -0300
@@ -615,6 +615,26 @@ fail:


 static ngx_slab_page_t *
+ngx_slab_merge_with_neighbour(ngx_slab_pool_t *pool, ngx_slab_page_t *page)
+{
+    ngx_slab_page_t *neighbour = &page[page->slab];
+    if (((ngx_slab_page_t *) neighbour->prev != NULL) && (neighbour->next
!= NULL) && ((neighbour->prev & NGX_SLAB_PAGE_MASK) == NGX_SLAB_PAGE)) {
+        page->slab += neighbour->slab;
+
+        ((ngx_slab_page_t *) neighbour->prev)->next = neighbour->next;
+        neighbour->next->prev = neighbour->prev;
+
+        neighbour->slab = NGX_SLAB_PAGE_FREE;
+        neighbour->prev = (uintptr_t) &pool->free;
+        neighbour->next = &pool->free;
+
+        return page;
+    }
+    return NULL;
+}
+
+
+static ngx_slab_page_t *
 ngx_slab_alloc_pages(ngx_slab_pool_t *pool, ngx_uint_t pages)
 {
     ngx_slab_page_t  *page, *p;
@@ -657,6 +677,19 @@ ngx_slab_alloc_pages(ngx_slab_pool_t *po
         }
     }

+    ngx_flag_t retry = 0;
+    for (page = pool->free.next; page != &pool->free;) {
+        if (ngx_slab_merge_with_neighbour(pool, page)) {
+            retry = 1;
+        } else {
+            page = page->next;
+        }
+    }
+
+    if (retry) {
+        return ngx_slab_alloc_pages(pool, pages);
+    }
+
     ngx_slab_error(pool, NGX_LOG_CRIT, "ngx_slab_alloc() failed: no
memory");

     return NULL;
@@ -687,6 +720,8 @@ ngx_slab_free_pages(ngx_slab_pool_t *poo
     page->next->prev = (uintptr_t) page;

     pool->free.next = page;
+
+    ngx_slab_merge_with_neighbour(pool, page);
 }






On Tue, Jul 30, 2013 at 7:09 AM, Maxim Dounin <mdounin at mdounin.ru> wrote:

> Hello!
>
> On Mon, Jul 29, 2013 at 04:01:37PM -0300, Wandenberg Peixoto wrote:
>
> [...]
>
> > What would be an alternative to not loop on pool->pages?
>
> Free memory blocks are linked in pool->free list, it should be
> enough to look there.
>
> [...]
>
> --
> Maxim Dounin
> http://nginx.org/en/donation.html
>
> _______________________________________________
> nginx-devel mailing list
> nginx-devel at nginx.org
> http://mailman.nginx.org/mailman/listinfo/nginx-devel
>
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