Am Montag, 24. Dezember 2018, 13:38:27 CET schrieb Chris Carson:
> TL;DR: hi! I'm a programmer! The attached patch to one line of code
> gives a 50% reduction in XML load CPU use! Skeptical? I was.
Dear Chris,
thanks a lot for this patch! I'm using gnucash since many years, too, and I'm
still somewhat unhappy with some of the reaction times in the 3.x series of
gnucash.
Now that you got a good catch on the XML loading time, maybe you are up for
some improvements on the XML saving time...? :-) I ran some valgrind where I
could locate an expensive code section, but I'm a bit out of practice to know
the C++11 way of writing that code in a more efficient way. Here's what I
found:
When saving to XML file, for each transaction the call stack with the
expensive code walks down like this:
gnc_transaction_dom_tree_create
add_time64
time64_to_dom_tree
gnc_print_time64
GncDateTime::format
GncDateTimeImpl::format
and this very last function seems significantly more expensive than needed,
slowing down saving considerably:
std::string
GncDateTimeImpl::format(const char* format) const
{
using Facet = boost::local_time::local_time_facet;
std::stringstream ss;
//The stream destructor frees the facet, so it must be heap-allocated.
auto output_facet(new Facet(normalize_format(format).c_str()));
// FIXME Rather than imbueing a locale below we probably should set
std::locale::global appropriately somewhere.
ss.imbue(std::locale(std::locale(""), output_facet));
ss << m_time;
return ss.str();
}
Both the operator<< and the constructor std::locale(const char*) seem to be
quite costly operations. To me, it seems there is way too much construction/
destruction going on for options that are constant during each saving
operation. Maybe even the recent commit 7f1a7115 (Frank?) has slowed down
things here even more. Maybe this could be checked in some of the unittests
more easily, but I'm a bit out of practice there, too. Maybe someone is up for
some performance boosting here...? Thanks a lot in advance!
Best Regards,
Christian
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