Re: Emacs repository benchmark: bzr and git

[Eli Zaretskii]

> Date: Tue, 18 Mar 2008 22:03:46 +0530
> From: dhruva <address@hidden>
> Cc: address@hidden, Teemu Likonen <address@hidden>,
>       address@hidden
> 
> address@hidden ~/stub/repo/bzr/emacs/trunk
> $ time bzr log -l 10 --short > :NUL
> 
> real    0m18.421s
> user    0m0.047s
> sys     0m0.031s
> 
> address@hidden ~/stub/repo/bzr/emacs/trunk
> $ time bzr log -l 10 --short > :NUL
> 
> real    0m18.375s
> user    0m0.015s
> sys     0m0.000s
> 
> 
> Even with 3 runs, I do not see any noticeable change in performance. I
> am running the tests on emacs repo. I am running all tests on M$-XP
> box (lenovo T61 series with Intel Centrino Pro, 1Gb RAM).
> 
> How do I get rid of cache if I have to restart the tests? I plan to
> analyze the '--lsprof' output to see if there is different code path
> and the so called hot/cold cache making any difference.

I'm just guessing, but judging from your results, it doesn't look like
the times are I/O-bound, and so the cold/hot cache issue is not an
important factor with bzr, at least on MS-Windows.  With I/O-bound
operations, there's a significant difference (factors of 5 to 20)
between the first and the second invocations, which is not the case
here.

Also, I'm guessing that the user/system times are irrelevant because
bzr invokes subsidiary processes that do the actual work (and the
Windows version of system calls used by `time' does not cover time
spent in child processes, unlike the Posix system calls).  That is the
only way I can understand the startling difference between the elapsed
time and the sum of system+user time.  So it's hard to tell where does
bzr spend most of its time from these numbers.