Split up documentation further. Add lpsm_need_checkpoint local variable.

1 files changed, 12 insertions, 1 deletions

diff --git a/arena.c b/arena.c
index 6c5a1b0..335400c 100644
--- a/arena.c
+++ b/arena.c
@@ -47,6 +47,11 @@
  */
 struct lpsm_arena *lpsm_memory_info = NULL;
 
+/*
+ * This variable is set when the persistent memory is dirty.
+ */
+sig_atomic_t lpsm_need_checkpoint;
+
 /* Wrappers for read() and write() which retries if incomplete */
 static ssize_t lpsm_read(int fd, void *buf, size_t count)
 {
@@ -159,6 +164,7 @@ static void lpsm_sigsegv(int signal, siginfo_t *siginfo, void *ptr)
   case page_clean:
     *pageinfo = page_dirty;	/* Page now dirty */
     PM->dirty_count++;		/* For accounting purposes */
+    lpsm_need_checkpoint = 1;	/* For user programs */
     /* Leave page r/w */
     break;
 
@@ -407,6 +413,7 @@ void *lpsm_arena_init(const char *main_file, const char *log_file,
 
   /* All pages clean at this time */
   memset(PM->pageinfo, page_clean, len_pages);
+  lpsm_need_checkpoint = 0;
 
   sigact.sa_sigaction = lpsm_sigsegv;
   sigemptyset(&sigact.sa_mask);
@@ -512,6 +519,9 @@ pid_t lpsm_checkpoint(double gc_factor, enum psmsync wait)
     }
   }
 
+  if ( !lpsm_need_checkpoint )
+    return 0;			/* If not dirty, don't fork */
+
   f = fork();
   if ( f == (pid_t)-1 )
     return (pid_t)-1;		/* Checkpoint failed! */
@@ -522,7 +532,8 @@ pid_t lpsm_checkpoint(double gc_factor, enum psmsync wait)
        array for a while. */
     mprotect(PM->arena, PM->arena_len, PROT_READ);
     memset(PM->pageinfo, page_clean, PM->arena_len >> PM->pageshift);
-    
+    lpsm_need_checkpoint = 0;
+
     PM->dirty_count = 0;	/* No pages dirty */
     PM->fork_seq++;		/* Increase next sequence number */