** Also affects: ubuntu-z-systems
Importance: Undecided
Status: New
** Changed in: ubuntu-z-systems
Status: New => Triaged
** Changed in: ubuntu-z-systems
Importance: Undecided => High
** Changed in: ubuntu-z-systems
Assignee: (unassigned) => Canonical Kernel Team (canonical-kernel-team)
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https://bugs.launchpad.net/bugs/1775391
Title:
kernel: Fix arch random implementation
Status in Ubuntu on IBM z Systems:
Triaged
Status in linux package in Ubuntu:
New
Bug description:
Description: kernel: Fix arch random implementation
Symptom: arch_get_random_seed_long() invocations may slow down the
interrupt handling on heavy interrupt producing loads.
Problem: The existing random device driver calls
arch_get_random_seed_long() in interrupt context. The
current implementation of this function uses the
PRNO(TRNG) instruction to provide good entropy. This
instruction is relatively slow and expensive and may
slow down the capacity of interrupts which can be handled
per cpu.
Solution: This fix reworks the arch_get_random_seed implementation.
It introduces a buffer concept to decouple the delivery
of random data via arch_get_random_seed*() from the
generation of new random bytes and so does not limit
the interrupt handling per cpu any more.
Reproduction: Systems with heavy irq load show performance decrease.
Component: kernel
Upstream commit(s): kernel 4.18
966f53e750aedc5f59f9ccae6bbfb8f671c7c842
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