File big-file-performance.patch of Package diffutils

Overview Repositories Revisions Requests Users Attributes Meta

File big-file-performance.patch of Package diffutils (Revision aff5c230a9678260d0ae341857888424)

Currently displaying revision aff5c230a9678260d0ae341857888424 , Show latest

From 68b82f6f8419a815cfcf962b3061352d414dc606 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Tue, 25 Oct 2016 21:57:56 -0700
Subject: [PATCH] diff: fix big performance degradation in 3.4

* NEWS, doc/diffutils.texi (Overview): Document this.
* src/analyze.c (diff_2_files): Restore too_expensive heuristic,
but this time with a floor that is 16 times the old floor.  This
should fix Bug#16848, by generating good-quality output for its
test case, while not introducing Bug#24715, by running nearly as
fast as diff-3.3 for that test case.
---
 NEWS               |  5 +++++
 doc/diffutils.texi |  5 ++++-
 src/analyze.c      | 11 ++++++++++-
 3 files changed, 19 insertions(+), 2 deletions(-)

Index: diffutils-3.5/src/analyze.c
===================================================================
--- diffutils-3.5.orig/src/analyze.c
+++ diffutils-3.5/src/analyze.c
@@ -534,6 +534,7 @@ diff_2_files (struct comparison *cmp)
     {
       struct context ctxt;
       lin diags;
+      lin too_expensive;
 
       /* Allocate vectors for the results of comparison:
 	 a flag for each line of each file, saying whether that line
@@ -565,11 +566,19 @@ diff_2_files (struct comparison *cmp)
 
       ctxt.heuristic = speed_large_files;
 
+      /* Set TOO_EXPENSIVE to be the approximate square root of the
+	 input size, bounded below by 4096.  4096 seems to be good for
+	 circa-2016 CPUs; see Bug#16848 and Bug#24715.  */
+      too_expensive = 1;
+      for (;  diags != 0;  diags >>= 2)
+	too_expensive <<= 1;
+      ctxt.too_expensive = MAX (4096, too_expensive);
+
       files[0] = cmp->file[0];
       files[1] = cmp->file[1];
 
       compareseq (0, cmp->file[0].nondiscarded_lines,
-		  0, cmp->file[1].nondiscarded_lines, &ctxt);
+		  0, cmp->file[1].nondiscarded_lines, minimal, &ctxt);
 
       free (ctxt.fdiag - (cmp->file[1].nondiscarded_lines + 1));

Places

File big-file-performance.patch of Package diffutils (Revision aff5c230a9678260d0ae341857888424)

Places