perf: make `hg perfwrite` more flexible

The more flexible command was used recently while finding a solution for a
buffering bug (eventually fixed in f9734b2d59cc (the changeset description uses
a different benchmark)).

In comparison to the previous version, the new version is much more flexible.
While using it, the focus was on testing small writes. For this reason, by
default it calls ui.write() 100 times with a single byte plus one newline byte,
for 100 lines.

To get the previous behavior, run `hg perfwrite --nlines=100000 --nitems=1
--item='Testing write performance' --batch-line`.

contrib/perf.py

@@ -3794,19 +3794,47 b' def perflrucache('
         fm.end()
 
 
-@command(b'perfwrite', formatteropts)
+@command(
+    b'perfwrite',
+    formatteropts
+    + [
+        (b'', b'write-method', b'write', b'ui write method'),
+        (b'', b'nlines', 100, b'number of lines'),
+        (b'', b'nitems', 100, b'number of items (per line)'),
+        (b'', b'item', b'x', b'item that is written'),
+        (b'', b'batch-line', None, b'pass whole line to write method at once'),
+        (b'', b'flush-line', None, b'flush after each line'),
+    ],
+)
 def perfwrite(ui, repo, **opts):
-    """microbenchmark ui.write
+    """microbenchmark ui.write (and others)
     """
     opts = _byteskwargs(opts)
 
+    write = getattr(ui, _sysstr(opts[b'write_method']))
+    nlines = int(opts[b'nlines'])
+    nitems = int(opts[b'nitems'])
+    item = opts[b'item']
+    batch_line = opts.get(b'batch_line')
+    flush_line = opts.get(b'flush_line')
+
+    if batch_line:
+        line = item * nitems + b'\n'
+
+    def benchmark():
+        for i in pycompat.xrange(nlines):
+            if batch_line:
+                write(line)
+            else:
+                for i in pycompat.xrange(nitems):
+                    write(item)
+                write(b'\n')
+            if flush_line:
+                ui.flush()
+        ui.flush()
+
     timer, fm = gettimer(ui, opts)
-
-    def write():
-        for i in range(100000):
-            ui.writenoi18n(b'Testing write performance\n')
-
-    timer(write)
+    timer(benchmark)
     fm.end()
 
 

relnotes/next

@@ -17,6 +17,10 b''
   was compiled against a OpenSSL version supporting TLS 1.1 or TLS 1.2
   (likely this requires the OpenSSL version to be at least 1.0.1).
 
+* The `hg perfwrite` command from contrib/perf.py was made more flexible and
+  changed its default behavior. To get the previous behavior, run `hg perfwrite
+  --nlines=100000 --nitems=1 --item='Testing write performance' --batch-line`.
+
 
 == Internal API Changes ==
 

tests/test-contrib-perf.t

@@ -180,7 +180,7 b' perfstatus'
    perfvolatilesets
                  benchmark the computation of various volatile set
    perfwalk      (no help text available)
-   perfwrite     microbenchmark ui.write
+   perfwrite     microbenchmark ui.write (and others)
   
   (use 'hg help -v perf' to show built-in aliases and global options)
   $ hg perfaddremove