glibc: memcpy calls in virtual guests are slower for x86_64 processors on RHEL 8 than RHEL 7

Solution Verified - Updated -

Issue

  • In virtual guests (i.e. VMware and KVM), RHEL 8's dd read is slower than RHEL 7:
# dd on RHEL 7
dd if=/tmp/read.tmp of=/dev/null
5368709120 bytes (5.4 GB) copied, 6.56411 s, 818 MB/s
# dd on RHEL8
dd if=/tmp/read.tmp of=/dev/null
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 1.84992 s, 580 MB/s

Environment

  • Red Hat Enterprise Linux 8
  • glibc, versions before 2.28-127.el8_3.2
  • virtual guest environments

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