##// END OF EJS Templates
posix: always seek to EOF when opening a file in append mode...
posix: always seek to EOF when opening a file in append mode Python 3 already does this, so skip it there. Consider the program: #include <stdio.h> int main() { FILE *f = fopen("narf", "w"); fprintf(f, "narf\n"); fclose(f); f = fopen("narf", "a"); printf("%ld\n", ftell(f)); fprintf(f, "troz\n"); printf("%ld\n", ftell(f)); return 0; } on macOS, FreeBSD, and Linux with glibc, this program prints 5 10 but on musl libc (Alpine Linux and probably others) this prints 0 10 By my reading of https://pubs.opengroup.org/onlinepubs/009695399/functions/fopen.html this is technically correct, specifically: > Opening a file with append mode (a as the first character in the > mode argument) shall cause all subsequent writes to the file to be > forced to the then current end-of-file, regardless of intervening > calls to fseek(). in other words, the file position doesn't really matter in append-mode files, and we can't depend on it being at all meaningful unless we perform a seek() before tell() after open(..., 'a'). Experimentally after a .write() we can do a .tell() and it'll always be reasonable, but I'm unclear from reading the specification if that's a smart thing to rely on. This matches what we do on Windows and what Python 3 does for free, so let's just be consistent. Thanks to Yuya for the idea.

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perf-revlog-write-plot.py
127 lines | 3.5 KiB | text/x-python | PythonLexer
/ contrib / perf-utils / perf-revlog-write-plot.py
#!/usr/bin/env python
#
# Copyright 2018 Paul Morelle <Paul.Morelle@octobus.net>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
#
# This script use the output of `hg perfrevlogwrite -T json --details` to draw
# various plot related to write performance in a revlog
#
# usage: perf-revlog-write-plot.py details.json
from __future__ import absolute_import, print_function
import json
import re
import numpy as np
import scipy.signal
from matplotlib import (
pyplot as plt,
ticker as mticker,
)
def plot(data, title=None):
items = {}
re_title = re.compile(r'^revisions #\d+ of \d+, rev (\d+)$')
for item in data:
m = re_title.match(item['title'])
if m is None:
continue
rev = int(m.group(1))
items[rev] = item
min_rev = min(items.keys())
max_rev = max(items.keys())
ary = np.empty((2, max_rev - min_rev + 1))
for rev, item in items.items():
ary[0][rev - min_rev] = rev
ary[1][rev - min_rev] = item['wall']
fig = plt.figure()
comb_plt = fig.add_subplot(211)
other_plt = fig.add_subplot(212)
comb_plt.plot(ary[0],
np.cumsum(ary[1]),
color='red',
linewidth=1,
label='comb')
plots = []
p = other_plt.plot(ary[0],
ary[1],
color='red',
linewidth=1,
label='wall')
plots.append(p)
colors = {
10: ('green', 'xkcd:grass green'),
100: ('blue', 'xkcd:bright blue'),
1000: ('purple', 'xkcd:dark pink'),
}
for n, color in colors.items():
avg_n = np.convolve(ary[1], np.full(n, 1. / n), 'valid')
p = other_plt.plot(ary[0][n - 1:],
avg_n,
color=color[0],
linewidth=1,
label='avg time last %d' % n)
plots.append(p)
med_n = scipy.signal.medfilt(ary[1], n + 1)
p = other_plt.plot(ary[0],
med_n,
color=color[1],
linewidth=1,
label='median time last %d' % n)
plots.append(p)
formatter = mticker.ScalarFormatter()
formatter.set_scientific(False)
formatter.set_useOffset(False)
comb_plt.grid()
comb_plt.xaxis.set_major_formatter(formatter)
comb_plt.legend()
other_plt.grid()
other_plt.xaxis.set_major_formatter(formatter)
leg = other_plt.legend()
leg2plot = {}
for legline, plot in zip(leg.get_lines(), plots):
legline.set_picker(5)
leg2plot[legline] = plot
def onpick(event):
legline = event.artist
plot = leg2plot[legline]
visible = not plot[0].get_visible()
for l in plot:
l.set_visible(visible)
if visible:
legline.set_alpha(1.0)
else:
legline.set_alpha(0.2)
fig.canvas.draw()
if title is not None:
fig.canvas.set_window_title(title)
fig.canvas.mpl_connect('pick_event', onpick)
plt.show()
if __name__ == '__main__':
import sys
if len(sys.argv) > 1:
print('reading from %r' % sys.argv[1])
with open(sys.argv[1], 'r') as fp:
plot(json.load(fp), title=sys.argv[1])
else:
print('reading from stdin')
plot(json.load(sys.stdin))