On Tue, Apr 2, 2013 at 7:34 PM, Cedric Blancher
<[email protected]> wrote:
> On 22 September 2012 10:14, Cedric Blancher
> <[email protected]> wrote:
>> On 17 September 2012 00:15, Roland Mainz <[email protected]> wrote:
>>> * Issues:
>>> - We have to make sure that memory allocation doesn't get excessive
>>> - Currently it seems that the stream returned by |sftmp()| somehow
>>> causes the shell not to use |mmap()| to read the temporary file's
>>> (used if we spill over or call an external process) content even for
>>> "insanely" (in this context :-) ) large file sizes (e.g. 2^20 bytes)
>>> ... erm... what exactlly causes this ?
>>
>> BTW: mmap() is not used for ANY files on Fedora Linux with a 64bit
>> ksh93. I've just observed that shcomp munches a 100MB script via
>> read() and not mmap(), which is IMO unfortunate.
>
> Roland, I recall you have a test module to monitor the mmap() usage
> for sfio I/O. Can you contribute this to Glenn and David, please?
Yes... but there are two issues:
1. I have to dig-out the test modules from an old machine... may take a few days
2. Command substitutions still do not use |mmap()| ... as this example
with ast-ksh.2013-04-02 on SuSE 12.2 Linux/AMD64/64bit shows:
-- snip --
$ strace ~/bin/ksh -c 'x=$(seq 400000) ; true' 2>&1 | fgrep 'read(' | wc -l
50
$ strace ~/bin/ksh -c 'x=$(seq 800000) ; true' 2>&1 | fgrep 'read(' | wc -l
92
$ strace ~/bin/ksh -c 'x=$(seq 1600000) ; true' 2>&1 | fgrep 'read(' | wc -l
187
-- snip --
Interesting question is... why does this happen ?
----
Bye,
Roland
--
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