On a related subject: it would be fantastic IMO to patch bash for z/OS so that it used local spawn and followed _BPX_SHAREAS rules. It would perform better and also allow you to use DD's in batch shell scripts like you can with the z/OS UNIX shell.
Unfortunately, bash is pretty complicated software, and updating it to do this is not at all easy because of the difference in semantics between fork()/exec() and spawn(). On Tue, Aug 27, 2019 at 7:54 AM David Crayford <dcrayf...@gmail.com> wrote: > On 2019-08-27 8:19 PM, David Crayford wrote: > > > > > > On 2019-08-27 8:13 PM, Andrew Rowley wrote: > >>> FWIW - debugging performance of forked Unix process startup/overhead > >>> is a > >>> mess - we had one customer who was seeing terrible performance when > >>> fork/execing tiny little shell processes that did practically > >>> nothing. It > >>> was only happening on one of their LPARs. The IBM Support center was > >>> involved for a really long time, and I don't know if they ever really > >>> figured out what was wrong. > >> > >> It wasn't running under the bash shell was it? I noticed that bash > >> has very significant overhead compared to the regular shell. > >> > >> I did some investigation using SMF data, and just wrote it up here: > >> > >> > https://www.blackhillsoftware.com/news/2019/08/27/comparing-bash-and-bin-sh-on-z-os/ > > > > > > Great write-up. Bash doesn't use local spawn so it always runs > > sub-processes in child address spaces. I have reported this so Rocket > > are aware > > and have opened a ticket. I'm not sure if it will be addressed anytime > > soon. Probably not. > > > Oops. Spoke too soon there! There is no "local" spawn as the job numbers > clearly show. How exactly are you deriving CPU time? Is it an > accumulation of SMF30CPT CPU times? > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
