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Message-ID: <CAN30aBHfWfozWZXR3uuzB2woCAES+qQa_eNcHDQSfHN4Dqj5WA@mail.gmail.com>
Date: Mon, 2 Feb 2026 23:17:33 -0800
From: Fangrui Song <i@...kray.me>
To: Fabian Rast <fabian.rast@....de>
Cc: Rich Felker <dalias@...c.org>, musl@...ts.openwall.com
Subject: Re: [PATCH v2] ldso: skip gnu hash calculation if precomputed
On Mon, Dec 22, 2025 at 10:40 AM Alexander Monakov <amonakov@...ras.ru> wrote:
>
>
> On Mon, 22 Dec 2025, Fabian Rast wrote:
>
> > /usr/lib/libwebkit2gtk-4.1.so.0
> > cycles: 234214481 (0.16) -> 224880118 (0.11) -3.99%
> > instructions: 329852233 (0.0) -> 233217195 (0.0) -29.3%
> > ref-cycles: 120347198 (1.09) -> 135856350 (0.6) 12.89%
> > duration_time: 62053249 (1.08) -> 69948475 (0.59) 12.72%
> >
> [...]
> >
> > Interestingly, there is a big regression in perfomance loading libwebkit2gtk
> > that i cannot explain...
>
> You have a reduction in actual CPU cycles (-4%, similar to others) and an
> increase of the reference counter cycles (and the matching increase in
> wall-clock time), which means that your CPU was running at a lower frequency
> in this test. If it is reproducible, perhaps it's an artifact of how CPU's
> automatic frequency scaling works: without the hashing loop, most of the
> remaining work is low-IPC (lots of TLB and cache misses), so maybe it doesn't
> raise clocks in this case. You can test e.g. by running at a fixed frequency.
>
> (you may already know, but just in case: cpupower tool can be used for
> requesting a fixed frequency with the 'performance' governor; to disable
> turbo clocks on AMD CPUs, write '0' to /sys/devices/system/cpu/cpufreq/boost )
>
> Thank you for your continued work on this!
>
> Alexander
Can the gh condition to optimized to
gh = !i1 || (i0 < i1 ? sym_index < i1 : sym_index >= i0) ? h0 : h1;
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