[pypy-commit] stmgc default: The nursery page's read markers are never read, but must still be writeable. We'd

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r1103:785dafe38e34
Date: 2014-03-27 14:07 +0100
http://bitbucket.org/pypy/stmgc/changeset/785dafe38e34/

Log:	The nursery page's read markers are never read, but must still be
	writeable. We'd like to map the pages to a general "trash page";
	missing one, we remap all the pages over to the same one. We still
	keep one page *per segment* to avoid cross-CPU cache conflicts.

diff --git a/c7/stm/core.h b/c7/stm/core.h
--- a/c7/stm/core.h
+++ b/c7/stm/core.h
@@ -28,6 +28,8 @@
 
 #define READMARKER_START      ((FIRST_OBJECT_PAGE * 4096UL) >> 4)
 #define FIRST_READMARKER_PAGE (READMARKER_START / 4096UL)
+#define OLD_RM_START          ((END_NURSERY_PAGE * 4096UL) >> 4)
+#define FIRST_OLD_RM_PAGE     (OLD_RM_START / 4096UL)
 #define NB_READMARKER_PAGES   (FIRST_OBJECT_PAGE - FIRST_READMARKER_PAGE)
 
 #define WRITELOCK_START       ((END_NURSERY_PAGE * 4096UL) >> 4)
diff --git a/c7/stm/pages.c b/c7/stm/pages.c
--- a/c7/stm/pages.c
+++ b/c7/stm/pages.c
@@ -169,25 +169,22 @@
     increment_total_allocated(total);
 }
 
+static void pages_setup_readmarkers_for_nursery(void)
+{
+    /* The nursery page's read markers are never read, but must still
+       be writeable.  We'd like to map the pages to a general "trash
+       page"; missing one, we remap all the pages over to the same one.
+       We still keep one page *per segment* to avoid cross-CPU cache
+       conflicts.
+    */
+    long i, j;
+    for (i = 1; i <= NB_SEGMENTS; i++) {
+        char *segment_base = get_segment_base(i);
 
-#if 0
-static bool is_fully_in_shared_pages(object_t *obj)
-{
-    uintptr_t first_page = ((uintptr_t)obj) / 4096UL;
-
-    if ((obj->stm_flags & GCFLAG_SMALL_UNIFORM) != 0)
-        return (flag_page_private[first_page] == SHARED_PAGE);
-
-    ssize_t obj_size = stmcb_size_rounded_up(
-        (struct object_s *)REAL_ADDRESS(stm_object_pages, obj));
-
-    uintptr_t last_page = (((uintptr_t)obj) + obj_size - 1) / 4096UL;
-
-    do {
-        if (flag_page_private[first_page++] != SHARED_PAGE)
-            return false;
-    } while (first_page <= last_page);
-
-    return true;
+        for (j = FIRST_READMARKER_PAGE + 1; j < FIRST_OLD_RM_PAGE; j++) {
+            remap_file_pages(segment_base + 4096 * j, 4096, 0,
+                             i * NB_PAGES + FIRST_READMARKER_PAGE, 0);
+            /* errors here ignored */
+        }
+    }
 }
-#endif
diff --git a/c7/stm/pages.h b/c7/stm/pages.h
--- a/c7/stm/pages.h
+++ b/c7/stm/pages.h
@@ -39,6 +39,7 @@
 static void page_privatize(uintptr_t pagenum);
 static void page_reshare(uintptr_t pagenum);
 static void _page_do_reshare(long segnum, uintptr_t pagenum);
+static void pages_setup_readmarkers_for_nursery(void);
 
 /* Note: don't ever do "mutex_pages_lock(); mutex_lock()" in that order */
 static void mutex_pages_lock(void);
diff --git a/c7/stm/setup.c b/c7/stm/setup.c
--- a/c7/stm/setup.c
+++ b/c7/stm/setup.c
@@ -36,6 +36,7 @@
                      (FIRST_READMARKER_PAGE - 2) * 4096UL,
                      PROT_NONE);
     }
+    pages_setup_readmarkers_for_nursery();
 }
 
 void stm_setup(void)