Hi Morten, At 2026-03-17T10:16:16+0100, Morten Bo Johansen wrote: > On 2026-03-17 G. Branden Robinson wrote: > > At 2026-03-16T19:19:04-0500, G. Branden Robinson wrote: > > An Arch Linux user has reported a performance regression in man page > > rendering in groff 1.24. For "small" man pages (or collections > > thereof), it's not noticeable, but the reported degradation is > > quadratic in large inputs, roughly twice as bad as one would expect > > for 25 copies in a row of the gcc man page. > > > > I'm not able to reproduce the problem. > > I get these numbers: > > 1 0.07 0.08 > 2 0.14 0.17 > 4 0.27 0.41 > 8 0.54 1.06 > 16 1.10 5.03 > 32 2.17 20.80 > 64 4.52 79.39
That's pretty hellacious. > % uname -a > Linux mathilde 6.18.18-1-lts #1 SMP PREEMPT_DYNAMIC Fri, 13 Mar 2026 20:22:24 > +0000 x86_64 GNU/Linux > > I am also using Arch Linux. What libc and libstdc++/libc++ does your system use? > I seemed to nail the performance regression down to this commit: > > 10 months ago 732b07d G. Branden Robinson ∙ [man]: Fix Savannah > #65190 (1/2) That's the same commit identified in Savannah #68145. But I think it may be a case of a change _exposing_ a latent bug (or, in this case, unperformant selection of an alogorithm or data structure) rather than the change _causing_ the problem. (That distinction may ring a bell for readers of this list. :) ) > Hope this is useful. Can you re-run your test scenario with the `-Z` option added to groff's command line? I'm curious to know how cutting grotty out of the execution pipeline affects the numbers. Regards, Branden
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