From: Martin Pool <mbp@samba.org>
Date: Mon, 8 Apr 2002 08:39:03 +0000 (+0000)
Subject: Notes on MD4 performance.  This quite unnecessarily takes up 90% of
X-Git-Url: https://mattmccutchen.net/rsync/rsync.git/commitdiff_plain/bd0ad74f4b2e517996fa681b807d5bc660e00ba4

Notes on MD4 performance.  This quite unnecessarily takes up 90% of
CPU on a local transfer, without achieving anything useful.
---

diff --git a/TODO b/TODO
index a24ef7a9..5a01a53d 100644
--- a/TODO
+++ b/TODO
@@ -451,6 +451,30 @@ Check "refuse options works"
   Was this broken when we changed to popt?
 
 
+PERFORMANCE ----------------------------------------------------------
+
+MD4 file_sum
+
+  If we're doing a local transfer, or using -W, then perhaps don't
+  send the file checksum.  If we're doing a local transfer, then
+  calculating MD4 checksums uses 90% of CPU and is unlikely to be
+  useful.
+
+  Indeed for transfers over zlib or ssh we can also rely on the
+  transport to have quite strong protection against corruption.
+
+  Perhaps we should have an option to disable this, analogous to
+  --whole-file, although it would default to disabled.  The file
+  checksum takes up a definite space in the protocol -- we can either
+  set it to 0, or perhaps just leave it out.
+
+MD4
+
+  Perhaps borrow an assembler MD4 from someone?
+
+  Make sure we call MD4 with properly-sized blocks whenever possible
+  to avoid copying into the residue region?
+
 String area code
 
   Test whether this is actually faster than just using malloc().  If