From: Bjorn Helgaas <bjorn.helgaas@hp.com>
To: Ingo Molnar <mingo@redhat.com>
Cc: linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: boot-time slowdown for measure_migration_cost
Date: Fri, 27 Jan 2006 21:03:27 +0000 [thread overview]
Message-ID: <200601271403.27065.bjorn.helgaas@hp.com> (raw)
The boot-time migration cost auto-tuning stuff seems to have
been merged to Linus' tree since 2.6.15. On little one- or
two-processor systems, the time required to measure the
migration costs isn't very noticeable, but by the time we
get to even a four-processor ia64 box, it adds about
30 seconds to the boot time, which seems like a lot.
Is that expected? Is the information we get really worth
that much? Could the measurement be done at run-time
instead? Is there a smaller hammer we could use, e.g.,
flushing just the buffer rather than the *entire* cache?
Did we just implement sched_cacheflush() incorrectly for
ia64?
Only ia64, x86, and x86_64 currently have a non-empty
sched_cacheflush(), and the x86* ones contain only "wbinvd()".
So I suspect that only ia64 sees this slowdown. But I would
guess that other arches will implement it in the future.
Bjorn
next reply other threads:[~2006-01-27 21:03 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-27 21:03 Bjorn Helgaas [this message]
2006-01-27 21:48 ` boot-time slowdown for measure_migration_cost Luck, Tony
2006-01-27 22:08 ` Prarit Bhargava
2006-01-30 17:21 ` Ingo Molnar
2006-01-30 18:53 ` Luck, Tony
2006-01-30 19:24 ` Ingo Molnar
2006-01-30 20:00 ` Luck, Tony
2006-01-30 20:43 ` Prarit Bhargava
2006-01-30 20:52 ` Prarit Bhargava
2006-01-30 20:43 ` John Hawkes
2006-01-30 19:26 ` Chen, Kenneth W
2006-02-01 0:50 ` Chuck Ebbert
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