From: Nathan Lynch <nathanl@linux.ibm.com>
To: Haren Myneni <haren@linux.ibm.com>,
mpe@ellerman.id.au, npiggin@gmail.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc/pseries: Move vas_migration_handler early during migration
Date: Thu, 22 Sep 2022 07:14:57 -0500 [thread overview]
Message-ID: <87czbnr4fy.fsf@linux.ibm.com> (raw)
In-Reply-To: <d8efade91dda831c9ed4abb226dab627da594c5f.camel@linux.ibm.com>
Haren Myneni <haren@linux.ibm.com> writes:
> When the migration is initiated, the hypervisor changes VAS
> mappings as part of pre-migration event. Then the OS gets the
> migration event which closes all VAS windows before the migration
> starts. NX generates continuous faults until windows are closed
> and the user space can not differentiate these NX faults coming
> from the actual migration. So to reduce this time window, close
> VAS windows first in pseries_migrate_partition().
I'm concerned that this is only narrowing a window of time where
undesirable faults occur, and that it may not be sufficient for all
configurations. Migrations can be in progress for minutes or hours,
while the time that we wait for the VASI state transition is usually
seconds or minutes. So I worry that this works around a problem in
limited cases but doesn't cover them all.
Maybe I don't understand the problem well enough. How does user space
respond to the NX faults?
next prev parent reply other threads:[~2022-09-22 12:15 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-22 8:27 [PATCH] powerpc/pseries: Move vas_migration_handler early during migration Haren Myneni
2022-09-22 12:14 ` Nathan Lynch [this message]
2022-09-23 8:37 ` Haren Myneni
2022-09-24 0:11 ` Nathan Lynch
2022-10-04 13:25 ` Michael Ellerman
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