[Bug nptl/23962] New: Very high overhead pthread_spin_lock on multi-node NUMA systems

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=23962

            Bug ID: 23962
           Summary: Very high overhead pthread_spin_lock on multi-node
                    NUMA systems
           Product: glibc
           Version: 2.29
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: hjl.tools at gmail dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---
            Target: x86-64

Created attachment 11437
  --> https://sourceware.org/bugzilla/attachment.cgi?id=11437&action=edit
A workload with pthread_spin_lock

This workload with pthread_spin_lock shows that:

[hjl@gnu-4 numa-spinlock]$ make tst-spinlock-overhead
gcc -O2 -g   -c -o tst-spinlock-overhead.o tst-spinlock-overhead.c
gcc -o tst-spinlock-overhead tst-spinlock-overhead.o -lpthread
[hjl@gnu-4 numa-spinlock]$ ./tst-spinlock-overhead
Number of threads:    2, Total time      193871694, Overhead: 3.17
Number of threads:    4, Total time      543029933, Overhead: 4.44
Number of threads:    8, Total time     2523646854, Overhead: 10.32
Number of threads:   16, Total time    11818665838, Overhead: 24.16
Number of threads:   32, Total time    66807641075, Overhead: 68.30
Number of threads:   48, Total time   151027783404, Overhead: 102.93
Number of threads:   56, Total time   167319124315, Overhead: 97.74
[hjl@gnu-4 numa-spinlock]$ 

when a spinlock is shared by threads running on different NUMA nodes,
spinlock overheads dominate CPU usages.  This makes multi-threaded
applications with spinlock run poorly on multi-node NUMA systems:

[hjl@gnu-4 numa-spinlock]$ cat /sys/devices/system/node/online
0-1
[hjl@gnu-4 numa-spinlock]$ cat /sys/devices/system/cpu/online
0-55
[hjl@gnu-4 numa-spinlock]$

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