Your message dated Fri, 02 Jul 2021 14:49:51 +0000
with message-id <e1lzkuj-0000wj...@fasolo.debian.org>
and subject line Bug#990573: fixed in pmdk 1.11.0-1
has caused the Debian Bug report #990573,
regarding libpmem1: insufficient flushing on ARMv8.2+
to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
(NB: If you are a system administrator and have no idea what this
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misconfiguration somewhere. Please contact ow...@bugs.debian.org
immediately.)
--
990573: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=990573
Debian Bug Tracking System
Contact ow...@bugs.debian.org with problems
--- Begin Message ---
Package: libpmem1
Version: 1.10-1
Severity: grave
Justification: causes data loss
[a fix is coming, filing this bug so the Release Team knows why]
Hi!
Support for arm64 in PMDK is deeply experimental. As far as I know, it has
never been tested on real hardware nor had been reviewed by someone with
adequate knowledge about ARM. Yet, enabling arm64 in our packages has been
requested multiple times, and bullseye / buster-backports do include arm64
builds. This was done with porting in mind, yet it looks like pmem-capable
ARM hardware is coming soon, and will be used in production not long after.
This makes inadequate support for new ARM chips unfortunate to say the least.
In ARMv8.0 and ARMv8.1, the only flushes available were CVAI (to make icache
= dcache, irrelevant for pmem), and CVAC ("flush to coherency"). The latter
was the deepest flush available, and implementors simply had no other option
than to have this instruction request the memory controller to send its data
to actual memory chips.
This changed in ARMv8.2, where a new instruction CVAP ("flush to
persistency") has been added, and CVAC was defined to require coherency only
between "agents" (such as CPU cores, GPU, etc) but not memory.
Yet PMDK knew only about CVAC -- despite asking around, no one of us could
get hold of an ARMv8.2 machine to implement detection/etc. Such support is
obviously not a priority for Intel nor IBM.
Only recently, I managed to get access to such a box, and implemented
flushes via CVAP. Without them, an unexpected power loss may result in
recent writes being lost. This is even worse than with disks -- a typical
filesystem will flush every 5 seconds or so, while there's no time-based
mechanism to flush CPU caches. If a machine finished its task and became
quiescent, it's possible the kernel and daemons won't actively touch more
than 16-64MB of L3 cache for hours or days.
The new flushes have been merged upstream in 1.11, I'm about to cherry-pick
to 1.10 for Bullseye.
Meow!
-- System Information:
Debian Release: 11.0
APT prefers unstable-debug
APT policy: (500, 'unstable-debug'), (500, 'unstable'), (500, 'testing'),
(500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 5.13.0-00032-g2fc675a48a0e (SMP w/64 CPU threads)
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)
Versions of packages libpmem1 depends on:
ii libc6 2.31-12
ii libdaxctl1 71.1-1
ii libndctl6 71.1-1
libpmem1 recommends no packages.
libpmem1 suggests no packages.
-- no debconf information
--- End Message ---
--- Begin Message ---
Source: pmdk
Source-Version: 1.11.0-1
Done: Adam Borowski <kilob...@angband.pl>
We believe that the bug you reported is fixed in the latest version of
pmdk, which is due to be installed in the Debian FTP archive.
A summary of the changes between this version and the previous one is
attached.
Thank you for reporting the bug, which will now be closed. If you
have further comments please address them to 990...@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.
Debian distribution maintenance software
pp.
Adam Borowski <kilob...@angband.pl> (supplier of updated pmdk package)
(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmas...@ftp-master.debian.org)
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
Format: 1.8
Date: Fri, 02 Jul 2021 15:23:11 +0200
Source: pmdk
Architecture: source
Version: 1.11.0-1
Distribution: experimental
Urgency: medium
Maintainer: Adam Borowski <kilob...@angband.pl>
Changed-By: Adam Borowski <kilob...@angband.pl>
Closes: 990573
Changes:
pmdk (1.11.0-1) experimental; urgency=medium
.
* New upstream release.
+ Fixes insufficient flushing on ARMv8.2+ (closes: #990573).
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--- End Message ---
