From: Hongyan Xia <hx242@xen.org>
To: Wei Liu <wl@xen.org>
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
julien@xen.org, "Andrew Cooper" <andrew.cooper3@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Jan Beulich" <jbeulich@suse.com>,
xen-devel@lists.xenproject.org,
"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [PATCH 00/16] Remove the direct map
Date: Fri, 01 May 2020 14:53:08 +0100 [thread overview]
Message-ID: <689a7c860a8a551e3b6009b16590e812dbf21055.camel@xen.org> (raw)
In-Reply-To: <20200501120715.hjak2gjp7ialwfq5@liuwe-devbox-debian-v2.j3c5onc20sse1dnehy4noqpfcg.zx.internal.cloudapp.net>
On Fri, 2020-05-01 at 12:07 +0000, Wei Liu wrote:
> On Thu, Apr 30, 2020 at 09:44:09PM +0100, Hongyan Xia wrote:
> > From: Hongyan Xia <hongyxia@amazon.com>
> >
> > This series depends on Xen page table domheap conversion:
> >
https://lists.xenproject.org/archives/html/xen-devel/2020-04/msg01374.html
> > .
> >
> > After breaking the reliance on the direct map to manipulate Xen
> > page
> > tables, we can now finally remove the direct map altogether.
> >
> > This series:
> > - fixes many places that use the direct map incorrectly or assume
> > the
> > presence of an always-mapped direct map in a wrong way.
> > - includes the early vmap patches for global mappings.
> > - initialises the mapcache for all domains, disables the fast path
> > that
> > uses the direct map for mappings.
> > - maps and unmaps xenheap on-demand.
> > - adds a boot command line switch to enable or disable the direct
> > map.
> >
> > This previous version was in RFC state and can be found here:
> >
https://lists.xenproject.org/archives/html/xen-devel/2019-09/msg02647.html
> > ,
> > which has since been broken into small series.
>
> OOI have you done any performance measurements?
>
> Seeing that now even guest table needs mapping / unmapping during
> restore, I'm curious to know how that would impact performance.
I actually have a lot of performance numbers but unfortunately on an
older version of Xen, not staging. I need to evaluate it again before
coming back to you. As you suspected, one strong signal from the
performance results is definitely the impact of walking guest tables.
For EPT, mapping and unmapping 20 times is no fun. This shows up in
micro-benchmarks, although larger benchmarks tend to be fine.
My question is, do we care about hiding EPT? I think it is fine to just
use xenheap pages (or any other form which does the job) so that we go
down from 20 mappings to only 4. I have done this hack with EPT and saw
significantly reduced impact for HVM guests in micro-benchmarks.
Hongyan
next prev parent reply other threads:[~2020-05-01 13:53 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-30 20:44 [PATCH 00/16] Remove the direct map Hongyan Xia
2020-04-30 20:44 ` [PATCH 01/16] x86/setup: move vm_init() before acpi calls Hongyan Xia
2020-04-30 20:44 ` [PATCH 02/16] acpi: vmap pages in acpi_os_alloc_memory Hongyan Xia
2020-05-01 12:02 ` Wei Liu
2020-05-01 12:46 ` Hongyan Xia
2020-05-01 21:35 ` Julien Grall
2020-05-04 8:27 ` Hongyan Xia
2020-04-30 20:44 ` [PATCH 03/16] x86/numa: vmap the pages for memnodemap Hongyan Xia
2020-04-30 20:44 ` [PATCH 04/16] x86/srat: vmap the pages for acpi_slit Hongyan Xia
2020-11-30 10:16 ` Jan Beulich
2020-11-30 18:11 ` Hongyan Xia
2020-12-01 7:37 ` Jan Beulich
2020-04-30 20:44 ` [PATCH 05/16] x86: map/unmap pages in restore_all_guests Hongyan Xia
2020-04-30 20:44 ` [PATCH 06/16] x86/pv: domheap pages should be mapped while relocating initrd Hongyan Xia
2020-04-30 20:44 ` [PATCH 07/16] x86/pv: rewrite how building PV dom0 handles domheap mappings Hongyan Xia
2020-04-30 20:44 ` [PATCH 08/16] x86: add Persistent Map (PMAP) infrastructure Hongyan Xia
2020-04-30 20:44 ` [PATCH 09/16] x86: lift mapcache variable to the arch level Hongyan Xia
2020-04-30 20:44 ` [PATCH 10/16] x86/mapcache: initialise the mapcache for the idle domain Hongyan Xia
2020-04-30 20:44 ` [PATCH 11/16] x86: add a boot option to enable and disable the direct map Hongyan Xia
2020-05-01 8:43 ` Julien Grall
2020-05-01 12:11 ` Wei Liu
2020-05-01 12:59 ` Hongyan Xia
2020-05-01 13:11 ` Wei Liu
2020-05-01 15:59 ` Julien Grall
2020-04-30 20:44 ` [PATCH 12/16] x86/domain_page: remove the fast paths when mfn is not in the directmap Hongyan Xia
2020-04-30 20:44 ` [PATCH 13/16] xen/page_alloc: add a path for xenheap when there is no direct map Hongyan Xia
2020-05-01 8:50 ` Julien Grall
2021-04-22 12:31 ` Jan Beulich
2021-04-28 11:04 ` Hongyan Xia
2021-04-28 11:51 ` Jan Beulich
2021-04-28 13:22 ` Hongyan Xia
2021-04-28 13:55 ` Jan Beulich
2020-04-30 20:44 ` [PATCH 14/16] x86/setup: leave early boot slightly earlier Hongyan Xia
2020-04-30 20:44 ` [PATCH 15/16] x86/setup: vmap heap nodes when they are outside the direct map Hongyan Xia
2020-04-30 20:44 ` [PATCH 16/16] x86/setup: do not create valid mappings when directmap=no Hongyan Xia
2020-05-01 12:07 ` [PATCH 00/16] Remove the direct map Wei Liu
2020-05-01 13:53 ` Hongyan Xia [this message]
2020-06-02 9:08 ` Wei Liu
2021-04-28 10:14 ` Hongyan Xia
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