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[PATCH 0/6] xen/x86: PV boot speedup
- To: Juergen Gross <jgross@xxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 30 Sep 2021 14:33:20 +0200
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, lkml <linux-kernel@xxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 30 Sep 2021 12:33:35 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
The observed (by the human eye) performance difference of early boot
between native and PV-on-Xen was just too large to not look into. As
it turns out, gaining performance back wasn't all that difficult.
While the series (re)introduces a small number of PTWR emulations on
the boot path (from phys_pte_init()), there has been a much larger
number of them post-boot. Hence I think if this was of concern, the
post-boot instances would want eliminating first.
Some of the later changes aren'r directly related to the main goal of
the series; these address aspects noticed while doing the investigation.
1: streamline set_pte_mfn()
2: restore (fix) xen_set_pte_init() behavior
3: adjust xen_set_fixmap()
4: adjust handling of the L3 user vsyscall special page table
5: there's no highmem anymore in PV mode
6: restrict PV Dom0 identity mapping
Jan
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