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Bug 1913750

Summary:	glibc: memcpy calls are slower for AMD processors on RHEL 8 than RHEL 7 [rhel-8.3.0.z]
Product:	Red Hat Enterprise Linux 8	Reporter:	RHEL Program Management Team <pgm-rhel-tools>
Component:	glibc	Assignee:	Florian Weimer <fweimer>
Status:	CLOSED ERRATA	QA Contact:	qe-baseos-tools-bugs
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	8.2	CC:	alanm, amike, ashankar, brclark, casantos, codonell, dj, fweimer, jaeshin, jwright, kdudka, mbliss, mcermak, mkolbas, mnewsome, pfrankli, sajan.karumanchi, sipoyare, skolosov, tnagata, vmukhame, yama, yoguma
Target Milestone:	rc	Keywords:	Bugfix, Patch, Triaged, ZStream
Target Release:	8.0	Flags:	pm-rhel: mirror+
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	glibc-2.28-127.el8_3.2	Doc Type:	Bug Fix
Doc Text:	Cause: On x86-64, the glibc implementation of string functions wrongly estimated the amount of last-level cache available to a thread. Consequence: Calling memcpy on large buffers could negatively impact overall cache performance of the system, or the memcpy call itself could be slow. Fix: The last-level cache size is no longer scaled with the number of reported hardware threads in the system. Result: The string functions bypass caches for large buffers (and only for large buffer), avoiding undue cache impact on the rest of the system.	Story Points:	---
Clone Of:	1880670	Environment:
Last Closed:	2021-02-16 14:36:33 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	1880670
Bug Blocks:	1913656

Comment 5 Florian Weimer 2021-01-13 12:49:29 UTC

*** Bug 1890830 has been marked as a duplicate of this bug. ***

Comment 11 errata-xmlrpc 2021-02-16 14:36:33 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (glibc bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:0556