[PATCH v2] Fix to avoid high memory footprint

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

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.

Signed-off-by: Harithamma D <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-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1744/HarithaIBM/memFootprintFix-v2
Pull-Request: https://github.com/git/git/pull/1744

Range-diff vs v1:

 1:  51c02f58fd6 ! 1:  500b7eacf2a Fix to avoid high memory footprint
     @@ Metadata
       ## Commit message ##
          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.
     +    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.
      
     -    Signed-off-by: Haritha D <harithamma.d@ibm.com>
     +    Signed-off-by: Harithamma D <harithamma.d@ibm.com>
      
       ## convert.c ##
      @@ convert.c: static void trace_encoding(const char *context, const char *path,
       	struct strbuf trace = STRBUF_INIT;
       	int i;
       
     -+	// If tracing is not on, exit early to avoid high memory footprint
     -+	if (!trace_pass_fl(&coe)) {
     ++	if (!trace_want(&coe))
      +		return;
     -+	}
      +
       	strbuf_addf(&trace, "%s (%s, considered %s):\n", context, path, encoding);
       	for (i = 0; i < len && buf; ++i) {

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