From: David Mosberger <davidm@napali.hpl.hp.com>
To: linux-ia64@vger.kernel.org
Subject: Re: [patch] Resched skip_rbs_switch to run 4 cycles faster on McKinley-type cores.
Date: Thu, 20 Jan 2005 06:50:07 +0000 [thread overview]
Message-ID: <16879.21663.445128.380686@napali.hpl.hp.com> (raw)
In-Reply-To: <200501190500.j0J505jY002441@napali.hpl.hp.com>
>>>>> On Thu, 20 Jan 2005 09:25:35 +1100, Keith Owens <kaos@sgi.com> said:
Keith> Damn, I was in the middle of developing a patch against this
Keith> area :(.
Oops.
Keith> Instead of being garbage when the interrupted code was in the
Keith> kernel, ar_bspstore and ar_rnat are set to zero. The test
Keith> for "do I skip_rbs_switch" changes from pUStk to "is saved
Keith> ar_bspstore non-zero".
Wouldn't this prevent user-level code from setting ar.bspstore to
zero? I'm not sure we should nail that into the kernel (by default
the first page is a NaT page, so it's not likely to be a real problem
as of today).
Keith> Comments?
Libunwind does support multiple register backing-stores, but since we
cannot unwind across firmware, I'm not sure whether this by itself
would make your life easier. If it would, let me know.
--david
next prev parent reply other threads:[~2005-01-20 6:50 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-01-19 5:00 [patch] Resched skip_rbs_switch to run 4 cycles faster on McKinley-type cores David Mosberger
2005-01-19 22:25 ` Keith Owens
2005-01-20 6:50 ` David Mosberger [this message]
2005-01-20 10:26 ` Keith Owens
2005-01-20 17:01 ` David Mosberger
2005-01-28 2:08 ` David Mosberger
2005-01-28 3:04 ` Keith Owens
2005-01-28 5:22 ` David Mosberger
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