Thanks for the clarification, Heitor!
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Title:
bcache: Performance degradation when querying priority_stats
Status in Linux:
Fix R
@pponnuvel stat(2) doesn't perform a read(2) on the file, so it won't
call the show() method for priority_stats (which was the problematic
call for this specific sysfs attribute).
In any case, this should be fixed in all supported Ubuntu series, so
even read(2) shouldn't be an issue anymore. Pleas
A question: Does stat(2) calls (lstat, fstat and the like) on priority_stats
cause the same issue?
Context: https://github.com/sosreport/sos/pull/2384#discussion_r563975063
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** Changed in: linux
Status: Fix Committed => Fix Released
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Title:
bcache: Performance degradation when querying priority_sta
This bug was fixed in the package linux - 5.3.0-24.26
---
linux (5.3.0-24.26) eoan; urgency=medium
* eoan/linux: 5.3.0-24.26 -proposed tracker (LP: #1852232)
* Eoan update: 5.3.9 upstream stable release (LP: #1851550)
- io_uring: fix up O_NONBLOCK handling for sockets
- d
This bug was fixed in the package linux - 4.4.0-168.197
---
linux (4.4.0-168.197) xenial; urgency=medium
* CVE-2018-12207
- KVM: x86: MMU: Encapsulate the type of rmap-chain head in a new struct
- KVM: x86: MMU: Consolidate quickly_check_mmio_pf() and
is_mmio_page_fault()
This bug was fixed in the package linux - 5.3.0-22.24
---
linux (5.3.0-22.24) eoan; urgency=medium
* [REGRESSION] md/raid0: cannot assemble multi-zone RAID0 with default_layout
setting (LP: #1849682)
- Revert "md/raid0: avoid RAID0 data corruption due to layout confusion."
This bug was fixed in the package linux - 5.0.0-35.38
---
linux (5.0.0-35.38) disco; urgency=medium
* [REGRESSION] md/raid0: cannot assemble multi-zone RAID0 with default_layout
setting (LP: #1849682)
- SAUCE: Fix revert "md/raid0: avoid RAID0 data corruption due to layout
This bug was fixed in the package linux - 4.15.0-69.78
---
linux (4.15.0-69.78) bionic; urgency=medium
* KVM NULL pointer deref (LP: #1851205)
- KVM: nVMX: handle page fault in vmread fix
* CVE-2018-12207
- KVM: MMU: drop vcpu param in gpte_access
- kvm: Convert kvm_l
Verified on eoan with test case from description:
# uname -r
5.3.0-20-generic
Performance kept steady throughout the priority_stat sysfs query.
** Tags removed: verification-needed-eoan
** Tags added: verification-done-eoan
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Verified on disco with test case from description:
# uname -r
5.0.0-33-generic
Write performance wasn't significantly affected in this test,
fluctuating between ~120MB/s and ~110MB/s.
** Tags removed: verification-needed-disco
** Tags added: verification-done-disco
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Verified on bionic with test case from description:
# uname -r
4.15.0-67-generic
Write performance dropped from ~150MB/s to ~147MB/s, and the system is
still responsive.
** Tags
Verified on xenial with test case from description:
# uname -r
4.4.0-167-generic
Bcache write performance wasn't affected significantly by the sysfs
query (~200MB/s to ~197MB/s), so the patch looks to be working fine.
** Tags removed: verification-needed-xenial
** Tags added: verification-done-xe
This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
eoan' to 'verification-done-eoan'. If the problem still exists, change
the tag 'verification
This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
xenial' to 'verification-done-xenial'. If the problem still exists,
change the tag 'verifica
This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
bionic' to 'verification-done-bionic'. If the problem still exists,
change the tag 'verifica
This bug is awaiting verification that the kernel in -proposed solves
the problem. Please test the kernel and update this bug with the
results. If the problem is solved, change the tag 'verification-needed-
disco' to 'verification-done-disco'. If the problem still exists, change
the tag 'verificati
** Changed in: linux (Ubuntu Xenial)
Status: New => Fix Committed
** Changed in: linux (Ubuntu Bionic)
Status: New => Fix Committed
** Changed in: linux (Ubuntu Disco)
Status: New => Fix Committed
** Changed in: linux (Ubuntu Eoan)
Status: In Progress => Fix Committed
** Also affects: linux (Ubuntu Eoan)
Importance: Undecided
Assignee: Heitor Alves de Siqueira (halves)
Status: In Progress
** Also affects: linux (Ubuntu Disco)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Xenial)
Importance: Undecided
Status
Patches sent to kernel-team list:
https://lists.ubuntu.com/archives/kernel-team/2019-October/104658.html
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Title:
bcache: Performance
Upstream commit:
https://git.kernel.org/linus/d55a4ae9e1af
** Changed in: linux
Status: In Progress => Fix Committed
** Changed in: linux (Ubuntu)
Status: Confirmed => In Progress
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** Description changed:
[Impact]
- Performance degradation for read/write workloads in bcache devices,
occasional system stalls
+ Querying bcache's priority_stats attribute in sysfs causes severe performance
degradation for read/write workloads and occasional system stalls
+
+ [Test Case]
+ N
** Tags added: canonical-bootstack
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Title:
bcache: Performance degradation when querying priority_stats
Status in Linux:
In Progr
The cond_resched() patch should make its way into the 5.4 merge window
(see bcache maintainer's reponse at [0]).
[0] https://lore.kernel.org/lkml/74950e24-245a-c627-0e2e-
32ac0b304...@suse.de/
** Also affects: linux
Importance: Undecided
Status: New
** Changed in: linux
Status:
I've uploaded comparison graphs at [0] to avoid decompressing the
.tar.gz archive. Complete logs and graphs from individual runs are in
the archive only, as they're too unwieldy to navigate.
[0] https://people.canonical.com/~halves/priority_stats/
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>From the comparison graphs, we can see that the impact of the sysfs
query is very significant for both read and write workloads. Taking just
the "sysfs" test from my previous comment into account:
In the random write tests:
* For 512b block sizes, we see about an 85% reduction in BW (down to ~2MB
This has been reported upstream as well, with a tentative patch in
https://lkml.org/lkml/2019/3/7/8
I've done some tests in fio to get some more data on this issue, with the
following scenarios:
- "raw" test -> fio test without any sysfs queries
- "sysfs" test -> fio + scripted sysfs querie
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