From: Juergen Gross <jgross@suse.com>
To: Wei Liu <wei.liu2@citrix.com>,
Xen-devel <xen-devel@lists.xenproject.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Jan Beulich <JBeulich@suse.com>
Subject: Re: [PATCH RFC 0/4] Use INVPCID to flush global mappings
Date: Thu, 15 Feb 2018 16:38:42 +0100 [thread overview]
Message-ID: <d0830e46-106d-29cb-aace-bfdfaa4c35d0@suse.com> (raw)
In-Reply-To: <20180215121040.20585-1-wei.liu2@citrix.com>
On 15/02/18 13:10, Wei Liu wrote:
> I wrote these patches sometime ago to explore PCID and INVPCID. I haven't
> thought through whether how to use both in Xen yet. But seeing Juergen laid out
> his thought on PCID and INVPCID I think some of the patches can be useful.
>
> I had done some benchmark on the speed in one of my older branch by inserting
> some trace points before and after the flush. It showed that twiddling CR4.PGE
> is 3 to 5 times slower than invpcid.
>
> This series is in incomplete -- obviously we have CR4.PGE twiddling in a few
> other places. But if you think it is beneficial I can try to convert those
> places as well.
I just did a little experiment by replacing the %cr4 based TLB flush in
Jan's XPTI patches by invpcid, on top of my last XPTI speedup patch (no
fancy ALTERNATIVE, just a plain replacement).
Doing a parallel build of the hypervisor in dom0 showed following data:
real user sys
xpti=no 61.2 167.7 71.9
xpti=yes 112.1 170.1 141.8
+ my speedup 103.0 171.2 131.2
+ invpcid 99.0 170.2 122.0
So system time reduction due to invpcid is quite nice.
Juergen
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prev parent reply other threads:[~2018-02-15 15:38 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-15 12:10 [PATCH RFC 0/4] Use INVPCID to flush global mappings Wei Liu
2018-02-15 12:10 ` [PATCH RFC 1/4] x86: introduce cpu_has_invpcid Wei Liu
2018-02-15 12:31 ` Jan Beulich
2018-02-15 12:10 ` [PATCH RFC 2/4] x86: report if PCID and INVPCID are supported Wei Liu
2018-02-15 12:10 ` [PATCH RFC 3/4] x86: add invpcid.h Wei Liu
2018-02-15 12:15 ` Andrew Cooper
2018-02-15 12:24 ` Wei Liu
2018-02-15 12:26 ` Andrew Cooper
2018-02-15 12:34 ` Jan Beulich
2018-02-15 12:35 ` Wei Liu
2018-02-15 13:23 ` Jan Beulich
2018-02-15 12:10 ` [PATCH RFC 4/4] x86: use invpcid to do global flush Wei Liu
2018-02-15 15:38 ` Juergen Gross [this message]
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