added posix_fadvise support (untested) ... this should help performance by

[rrdtool.git] / src / rrd_fetch.c

diff --git a/src/rrd_fetch.c b/src/rrd_fetch.c
index 5745892..7e92c2c 100644 (file)
--- a/src/rrd_fetch.c
+++ b/src/rrd_fetch.c
@@ -205,6 +205,7 @@ rrd_fetch_fn(
     rrd_t     rrd;
     rrd_value_t    *data_ptr;
     unsigned long  rows;
+    long  rrd_head_size;
 
 #ifdef DEBUG
 fprintf(stderr,"Entered rrd_fetch_fn() searching for the best match\n");
@@ -214,6 +215,8 @@ fprintf(stderr,"Looking for: start %10lu end %10lu step %5lu\n",
 
     if(rrd_open(filename,&in_file,&rrd, RRD_READONLY)==-1)
        return(-1);
+
+    rrd_head_size = ftell(in_file);
     
     /* when was the really last update of this file ? */
 
@@ -453,6 +456,16 @@ fprintf(stderr,"partial match, not best\n");
                fclose(in_file);
                return(-1);
            }
+#ifdef POSIX_FADVISE
+       /* don't pollute the buffer cache with data read from the file. We do this while reading to 
+          keep damage minimal */
+       if (0 != posix_fadvise(fileno(in_file), rrd_head_size, ftell(in_file), POSIX_FADV_DONTNEED)) {
+           rrd_set_error("setting POSIX_FADV_DONTNEED on '%s': %s",file_name, rrd_strerror(errno));
+           fclose(in_file);
+           return(-1);
+       } 
+#endif
+
 #ifdef DEBUG
            fprintf(stderr,"post fetch %li -- ",i);
            for(ii=0;ii<*ds_cnt;ii++)
@@ -467,6 +480,14 @@ fprintf(stderr,"partial match, not best\n");
        
     }
     rrd_free(&rrd);
+#ifdef POSIX_FADVISE
+    /* and just to be sure we drop everything except the header at the end */
+    if (0 != posix_fadvise(fileno(in_file), rrd_head_size, 0, POSIX_FADV_DONTNEED)) {
+           rrd_set_error("setting POSIX_FADV_DONTNEED on '%s': %s",file_name, rrd_strerror(errno));
+           fclose(in_file);
+           return(-1);
+    } 
+#endif     
     fclose(in_file);
     return(0);
 }