From: Simon Glass <simon.glass@canonical.com> The VT100 escape sequence filter is applied to the entire buffer on every read iteration, causing O(n^2) performance. With 1.6MB of output from verbose unit tests and 1KB reads, this results in ~1600 iterations, each processing an ever-growing buffer. Fix this by filtering only the newly received data before appending it to the buffer. To test this, dm_test_host() was modified to do 10 malloc_dump() calls, thus producing a lot of output. The impact of this patch is: total time 6s -> 4.5s total CPU 18s -> 13s Note: Various other approaches were tried, including removing the concatenation to self.buf and updating expect() to only consider recent text. None of these yielded useful results. Signed-off-by: Simon Glass <simon.glass@canonical.com> --- test/py/console_base.py | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/test/py/console_base.py b/test/py/console_base.py index 6d117413aa3..c4472420c31 100644 --- a/test/py/console_base.py +++ b/test/py/console_base.py @@ -813,11 +813,13 @@ class ConsoleBase(): c = self.p.receive(RECV_BUF_SIZE) if self.logfile_read: self.logfile_read.write(c) - self.buf += c + # Filter VT100 escapes from new data only, not entire buffer. + # This avoids O(n^2) behaviour when receiving large output. # count=0 is supposed to be the default, which indicates # unlimited substitutions, but in practice the version of # Python in Ubuntu 14.04 appears to default to count=2! - self.buf = self.re_vt100.sub('', self.buf, count=1000000) + c = self.re_vt100.sub('', c, count=1000000) + self.buf += c finally: if self.logfile_read: self.logfile_read.flush() -- 2.43.0