Re: [PATCH v2 2/4] fsmonitor: Don't bother pretty-printing JSON from watchman

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On 10/25/2017 9:31 PM, Alex Vandiver wrote:
This provides modest performance savings.  Benchmarking with the
following program, with and without `--no-pretty`, we find savings of
23% (0.316s -> 0.242s) in the git repository, and savings of 8% (5.24s
-> 4.86s) on a large repository with 580k files in the working copy.


Given this patch series is all about speed, it's good to see *any* wins - especially those that don't impact functionality at all. The performance win of --no-pretty is greater than I expected.

     #!/usr/bin/perl

     use strict;
     use warnings;
     use IPC::Open2;

     my $pid = open2(\*CHLD_OUT, \*CHLD_IN, "watchman -j @ARGV")
         or die "open2() failed: $!\n" .
         "Falling back to scanning...\n";

     my $query = qq|["query", "$ENV{PWD}", {}]|;

     print CHLD_IN $query;
     close CHLD_IN;
     my $response = do {local $/; <CHLD_OUT>};

     my $json_pkg;
     eval {
         require JSON::XSomething;
         $json_pkg = "JSON::XSomething";
         1;
     } or do {
         require JSON::PP;
         $json_pkg = "JSON::PP";
     };

     my $o = $json_pkg->new->utf8->decode($response);

Signed-off-by: Alex Vandiver <alexmv@xxxxxxxxxxx>
---
  t/t7519/fsmonitor-watchman                 | 2 +-
  templates/hooks--fsmonitor-watchman.sample | 2 +-
  2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/t/t7519/fsmonitor-watchman b/t/t7519/fsmonitor-watchman
index a3e30bf54..79f24325c 100755
--- a/t/t7519/fsmonitor-watchman
+++ b/t/t7519/fsmonitor-watchman
@@ -50,7 +50,7 @@ launch_watchman();
sub launch_watchman { - my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j')
+	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')

Since this is a test script performance isn't critical. This version of the integration script logs the response to a file in .git/watchman-response.json and is much more human readable without the "--no-pretty." As such, I'd leave this one pretty.

  	    or die "open2() failed: $!\n" .
  	    "Falling back to scanning...\n";
diff --git a/templates/hooks--fsmonitor-watchman.sample b/templates/hooks--fsmonitor-watchman.sample
index 9eba8a740..9a082f278 100755
--- a/templates/hooks--fsmonitor-watchman.sample
+++ b/templates/hooks--fsmonitor-watchman.sample
@@ -49,7 +49,7 @@ launch_watchman();
sub launch_watchman { - my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j')
+	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')

No human will see this response so the faster --no-pretty option makes sense.

  	    or die "open2() failed: $!\n" .
  	    "Falling back to scanning...\n";



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