[PATCH v6] convert: return early when not tracing

From: Haritha via GitGitGadget <gitgitgadget@gmail.com>
Date: Jul 31, 2024, 13:33 UTC
Message-ID: <pull.1744.v6.git.git.1722432839473.gitgitgadget@gmail.com>
In-Reply-To: <pull.1744.v5.git.git.1722310937061.gitgitgadget@gmail.com>

From: D Harithamma <harithamma.d@ibm.com>

When Git adds a file requiring encoding conversion and tracing of encoding conversion is not requested via the GIT_TRACE_WORKING_TREE_ENCODING environment variable, the `trace_encoding()` function still allocates & prepares "human readable" copies of the file contents before and after conversion to show in the trace. This results in a high memory footprint and increased runtime without providing any user-visible benefit.

This fix introduces an early exit from the `trace_encoding()` function when tracing is not requested, preventing unnecessary memory allocation and processing.

Signed-off-by: D Harithamma <harithamma.d@ibm.com>
---
    Fix to avoid high memory footprint
    
    This fix avoids high memory footprint when adding files that require
    conversion
    
    Git has a trace_encoding routine that prints trace output when
    GIT_TRACE_WORKING_TREE_ENCODING=1 is set. This environment variable is
    used to debug the encoding contents. When a 40MB file is added, it
    requests close to 1.8GB of storage from xrealloc which can lead to out
    of memory errors. However, the check for GIT_TRACE_WORKING_TREE_ENCODING
    is done after the string is allocated. This resolves high memory
    footprints even when GIT_TRACE_WORKING_TREE_ENCODING is not active. This
    fix adds an early exit to avoid the unnecessary memory allocation.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1744%2FHarithaIBM%2FmemFootprintFix-v6
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1744/HarithaIBM/memFootprintFix-v6
Pull-Request: https://github.com/git/git/pull/1744

Range-diff vs v5:

 1:  e2518b28f1c ! 1:  7b68aa9de1d convert: return early when not tracing
     @@ Commit message
          when tracing is not requested, preventing unnecessary memory allocation
          and processing.
      
     -    Signed-off-by: Harithamma D <harithamma.d@ibm.com>
     +    Signed-off-by: D Harithamma <harithamma.d@ibm.com>
      
       ## convert.c ##
      @@ convert.c: static void trace_encoding(const char *context, const char *path,

 convert.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/convert.c b/convert.c
index d8737fe0f2d..c4ddc4de81b 100644
--- a/convert.c
+++ b/convert.c
@@ -324,6 +324,9 @@ static void trace_encoding(const char *context, const char *path,
 	struct strbuf trace = STRBUF_INIT;
 	int i;
 
+	if (!trace_want(&coe))
+		return;
+
 	strbuf_addf(&trace, "%s (%s, considered %s):\n", context, path, encoding);
 	for (i = 0; i < len && buf; ++i) {
 		strbuf_addf(

base-commit: 557ae147e6cdc9db121269b058c757ac5092f9c9

-- 
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