Some more measurements in virtual machines with 8 CPUs: Debian 9 (glibc 2.24) 4 CPUs: 0.33 sec 8 CPUs: 0.34 sec Debian 10 (glibc 2.28) 4 CPUs: 23 sec 8 CPUs: 29 sec
So, while glibc < 2.25 did not prefer writers (like musl libc, OpenBSD 7.5, AIX), it's only starting with Torvald Riegel's rewrite of the rwlocks in glibc 2.25 [1] that writer starvation occurs massively. Bruno [1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=cc25c8b4c1196a8c29e9a45b1e096b99a87b7f8c
