From nelson@crynwr.com Sat Jul 23 15:19:58 2005
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	["1512" "Tuesday" "20" "April" "2004" "13:06:49" "+0200" "Lennert Buytenhek" "buytenh@wantstofly.org" nil "61" "patch to make djbdns 1.05 cache its mmap() of the data.cdb file" "^From:" nil nil "4" nil nil nil nil nil nil nil nil nil]
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From: Lennert Buytenhek <buytenh@wantstofly.org>
To: nelson@crynwr.com
Subject: patch to make djbdns 1.05 cache its mmap() of the data.cdb file
Date: Tue, 20 Apr 2004 13:06:49 +0200

Hi,

This patch makes djbdns 1.05 cache its mmap() of the data.cdb file up to a
maximum of one second.  Under high query load, this substantially reduces
the number of times that the database file needs to be mapped and unmapped,
and gives a two-digit percentage performance improvement under 100% system
load (as discussed on the djbdns mailing list.)

Could you stick a copy of the patch on www.tinydns.org please?  I don't
have anywhere to host it myself at this point, and I would like to see it
on that page -- is that acceptable to you?


thanks,
Lennert



diff -urN djbdns-1.05.orig/tdlookup.c djbdns-1.05/tdlookup.c
--- djbdns-1.05.orig/tdlookup.c	2001-02-11 22:11:45.000000000 +0100
+++ djbdns-1.05/tdlookup.c	2004-04-18 13:56:13.000000000 +0200
@@ -280,15 +280,24 @@
 
 int respond(char *q,char qtype[2],char ip[4])
 {
-  int fd;
+  static struct tai cdb_valid = { 0 };
+  static int fd = -1;
+  struct tai one_second;
   int r;
   char key[6];
 
   tai_now(&now);
-  fd = open_read("data.cdb");
-  if (fd == -1) return 0;
-  cdb_init(&c,fd);
-
+  if (tai_less(&cdb_valid, &now)) {
+    if (fd != -1) {
+      cdb_free(&c);
+      close(fd);
+    }
+    fd = open_read("data.cdb");
+    if (fd == -1) return 0;
+    cdb_init(&c,fd);
+    tai_uint(&one_second, 1);
+    tai_add(&cdb_valid, &now, &one_second);
+  }
   byte_zero(clientloc,2);
   key[0] = 0;
   key[1] = '%';
@@ -304,7 +313,5 @@
 
   r = doit(q,qtype);
 
-  cdb_free(&c);
-  close(fd);
   return r;
 }

----- End forwarded message -----