Re: Slow history load with some values of HISTSIZE

[alex xmb sw ratchev]

On Sat, Feb 10, 2024, 03:06 Chet Ramey <chet.ramey@case.edu> wrote:

> On 2/3/24 3:29 PM, Casey Johnson wrote:
>
> > Bash Version: 5.1
> > Patch Level: 16
> > Release Status: release
> >
> > Description:
> >
> > The current implementation of the command history takes a long time to
> load
> > a large HISTFILE when history is stifled.  This is because there is a
> > memmove() for every line of HISTFILE once HISTSIZE lines have been
> loaded.
> > If N is the number of lines in HISTFILE then the cost of the memmoves
> ends
> > up being something like (N - HISTSIZE) * HISTSIZE, peaking when HISTSIZE
> is
> > roughly N/2.
>
> Thanks for the report and the patch. I applied it with some tweaks and
> saw a dramatic performance improvement for very large history files (I
> tested with one that was about 690000 entries) where HISTSIZE is
> significantly smaller (I tested with HISTSIZE=100000): from around 11
> seconds to less than 0.3 seconds.
>

++ speed optimization

greets ++

Chet
>
> --
> ``The lyf so short, the craft so long to lerne.'' - Chaucer
>                  ``Ars longa, vita brevis'' - Hippocrates
> Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/
>
>