* [PATCH for-4.5] tools/libxc: Avoid cacheflush toolstack hypercalls on x86
@ 2014-09-24 13:47 Andrew Cooper
2014-09-24 14:22 ` Ian Campbell
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Cooper @ 2014-09-24 13:47 UTC (permalink / raw)
To: Xen-devel
Cc: Keir Fraser, Ian Campbell, Andrew Cooper, Ian Jackson,
Tim Deegan, Jan Beulich, Wei Liu
XEN_DOMCTL_cacheflush hypercalls are (and will always be) -ENOSYS on x86, but
xc_domain_cacheflush() is called often during domain build and migrate for
correct behaviour on ARM.
Stub xc_domain_cacheflush() out on x86 to remove its pressure on the global
domctl lock, and the hypercall overhead (which applies further pressure to the
already heavily-contended TLB flush lock).
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <JBeulich@suse.com>
CC: Tim Deegan <tim@xen.org>
CC: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
---
tools/libxc/xc_domain.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
index 1a6f90a..a68127f 100644
--- a/tools/libxc/xc_domain.c
+++ b/tools/libxc/xc_domain.c
@@ -51,12 +51,28 @@ int xc_domain_create(xc_interface *xch,
int xc_domain_cacheflush(xc_interface *xch, uint32_t domid,
xen_pfn_t start_pfn, xen_pfn_t nr_pfns)
{
+#if defined (__i386__) || defined (__x86_64__)
+ /*
+ * The x86 architecture provides cache coherency guarantees which prevent
+ * the need for this hypercall.
+ *
+ * This call however is made frequently during domain build and migrate
+ * for the benefit of ARM, where cache flushes are needed.
+ *
+ * Stub it out here on x86 as domctls take the global domctl lock in Xen
+ * which is detrimental to concurrent toolstack operations on other
+ * domains.
+ */
+ errno = ENOSYS;
+ return -1;
+#else
DECLARE_DOMCTL;
domctl.cmd = XEN_DOMCTL_cacheflush;
domctl.domain = (domid_t)domid;
domctl.u.cacheflush.start_pfn = start_pfn;
domctl.u.cacheflush.nr_pfns = nr_pfns;
return do_domctl(xch, &domctl);
+#endif
}
int xc_domain_pause(xc_interface *xch,
--
1.7.10.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH for-4.5] tools/libxc: Avoid cacheflush toolstack hypercalls on x86
2014-09-24 13:47 [PATCH for-4.5] tools/libxc: Avoid cacheflush toolstack hypercalls on x86 Andrew Cooper
@ 2014-09-24 14:22 ` Ian Campbell
2014-09-24 14:24 ` Andrew Cooper
0 siblings, 1 reply; 4+ messages in thread
From: Ian Campbell @ 2014-09-24 14:22 UTC (permalink / raw)
To: Andrew Cooper
Cc: Wei Liu, Ian Jackson, Tim Deegan, Xen-devel, Jan Beulich, Keir Fraser
On Wed, 2014-09-24 at 14:47 +0100, Andrew Cooper wrote:
> XEN_DOMCTL_cacheflush hypercalls are (and will always be) -ENOSYS on x86, but
> xc_domain_cacheflush() is called often during domain build and migrate for
> correct behaviour on ARM.
>
> Stub xc_domain_cacheflush() out on x86 to remove its pressure on the global
> domctl lock, and the hypercall overhead (which applies further pressure to the
> already heavily-contended TLB flush lock).
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Keir Fraser <keir@xen.org>
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Tim Deegan <tim@xen.org>
> CC: Ian Campbell <Ian.Campbell@citrix.com>
> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Although IMHO only the first paragraph of the comment is useful, the
rest belongs in the commit log (where it already mostly is already).
> ---
> tools/libxc/xc_domain.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
> index 1a6f90a..a68127f 100644
> --- a/tools/libxc/xc_domain.c
> +++ b/tools/libxc/xc_domain.c
> @@ -51,12 +51,28 @@ int xc_domain_create(xc_interface *xch,
> int xc_domain_cacheflush(xc_interface *xch, uint32_t domid,
> xen_pfn_t start_pfn, xen_pfn_t nr_pfns)
> {
> +#if defined (__i386__) || defined (__x86_64__)
> + /*
> + * The x86 architecture provides cache coherency guarantees which prevent
> + * the need for this hypercall.
> + *
> + * This call however is made frequently during domain build and migrate
> + * for the benefit of ARM, where cache flushes are needed.
> + *
> + * Stub it out here on x86 as domctls take the global domctl lock in Xen
> + * which is detrimental to concurrent toolstack operations on other
> + * domains.
> + */
> + errno = ENOSYS;
> + return -1;
> +#else
> DECLARE_DOMCTL;
> domctl.cmd = XEN_DOMCTL_cacheflush;
> domctl.domain = (domid_t)domid;
> domctl.u.cacheflush.start_pfn = start_pfn;
> domctl.u.cacheflush.nr_pfns = nr_pfns;
> return do_domctl(xch, &domctl);
> +#endif
> }
>
> int xc_domain_pause(xc_interface *xch,
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH for-4.5] tools/libxc: Avoid cacheflush toolstack hypercalls on x86
2014-09-24 14:22 ` Ian Campbell
@ 2014-09-24 14:24 ` Andrew Cooper
2014-09-24 14:29 ` Ian Campbell
0 siblings, 1 reply; 4+ messages in thread
From: Andrew Cooper @ 2014-09-24 14:24 UTC (permalink / raw)
To: Ian Campbell
Cc: Wei Liu, Ian Jackson, Tim Deegan, Xen-devel, Jan Beulich, Keir Fraser
On 24/09/14 15:22, Ian Campbell wrote:
> On Wed, 2014-09-24 at 14:47 +0100, Andrew Cooper wrote:
>> XEN_DOMCTL_cacheflush hypercalls are (and will always be) -ENOSYS on x86, but
>> xc_domain_cacheflush() is called often during domain build and migrate for
>> correct behaviour on ARM.
>>
>> Stub xc_domain_cacheflush() out on x86 to remove its pressure on the global
>> domctl lock, and the hypercall overhead (which applies further pressure to the
>> already heavily-contended TLB flush lock).
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> CC: Keir Fraser <keir@xen.org>
>> CC: Jan Beulich <JBeulich@suse.com>
>> CC: Tim Deegan <tim@xen.org>
>> CC: Ian Campbell <Ian.Campbell@citrix.com>
>> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
>> CC: Wei Liu <wei.liu2@citrix.com>
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
>
> Although IMHO only the first paragraph of the comment is useful, the
> rest belongs in the commit log (where it already mostly is already).
I am happy for that to be fixed while committing, or I could resubmit?
~Andrew
>
>> ---
>> tools/libxc/xc_domain.c | 16 ++++++++++++++++
>> 1 file changed, 16 insertions(+)
>>
>> diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
>> index 1a6f90a..a68127f 100644
>> --- a/tools/libxc/xc_domain.c
>> +++ b/tools/libxc/xc_domain.c
>> @@ -51,12 +51,28 @@ int xc_domain_create(xc_interface *xch,
>> int xc_domain_cacheflush(xc_interface *xch, uint32_t domid,
>> xen_pfn_t start_pfn, xen_pfn_t nr_pfns)
>> {
>> +#if defined (__i386__) || defined (__x86_64__)
>> + /*
>> + * The x86 architecture provides cache coherency guarantees which prevent
>> + * the need for this hypercall.
>> + *
>> + * This call however is made frequently during domain build and migrate
>> + * for the benefit of ARM, where cache flushes are needed.
>> + *
>> + * Stub it out here on x86 as domctls take the global domctl lock in Xen
>> + * which is detrimental to concurrent toolstack operations on other
>> + * domains.
>> + */
>> + errno = ENOSYS;
>> + return -1;
>> +#else
>> DECLARE_DOMCTL;
>> domctl.cmd = XEN_DOMCTL_cacheflush;
>> domctl.domain = (domid_t)domid;
>> domctl.u.cacheflush.start_pfn = start_pfn;
>> domctl.u.cacheflush.nr_pfns = nr_pfns;
>> return do_domctl(xch, &domctl);
>> +#endif
>> }
>>
>> int xc_domain_pause(xc_interface *xch,
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH for-4.5] tools/libxc: Avoid cacheflush toolstack hypercalls on x86
2014-09-24 14:24 ` Andrew Cooper
@ 2014-09-24 14:29 ` Ian Campbell
0 siblings, 0 replies; 4+ messages in thread
From: Ian Campbell @ 2014-09-24 14:29 UTC (permalink / raw)
To: Andrew Cooper
Cc: Wei Liu, Ian Jackson, Tim Deegan, Xen-devel, Jan Beulich, Keir Fraser
On Wed, 2014-09-24 at 15:24 +0100, Andrew Cooper wrote:
> On 24/09/14 15:22, Ian Campbell wrote:
> > On Wed, 2014-09-24 at 14:47 +0100, Andrew Cooper wrote:
> >> XEN_DOMCTL_cacheflush hypercalls are (and will always be) -ENOSYS on x86, but
> >> xc_domain_cacheflush() is called often during domain build and migrate for
> >> correct behaviour on ARM.
> >>
> >> Stub xc_domain_cacheflush() out on x86 to remove its pressure on the global
> >> domctl lock, and the hypercall overhead (which applies further pressure to the
> >> already heavily-contended TLB flush lock).
> >>
> >> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> >> CC: Keir Fraser <keir@xen.org>
> >> CC: Jan Beulich <JBeulich@suse.com>
> >> CC: Tim Deegan <tim@xen.org>
> >> CC: Ian Campbell <Ian.Campbell@citrix.com>
> >> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
> >> CC: Wei Liu <wei.liu2@citrix.com>
> > Acked-by: Ian Campbell <ian.campbell@citrix.com>
> >
> > Although IMHO only the first paragraph of the comment is useful, the
> > rest belongs in the commit log (where it already mostly is already).
>
> I am happy for that to be fixed while committing, or I could resubmit?
If you think it's just a case of nuking the other two paras then I'll do
it on commit, if you want to add some other words to the commit message
best to resubmit.
Ian.
>
> ~Andrew
>
> >
> >> ---
> >> tools/libxc/xc_domain.c | 16 ++++++++++++++++
> >> 1 file changed, 16 insertions(+)
> >>
> >> diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
> >> index 1a6f90a..a68127f 100644
> >> --- a/tools/libxc/xc_domain.c
> >> +++ b/tools/libxc/xc_domain.c
> >> @@ -51,12 +51,28 @@ int xc_domain_create(xc_interface *xch,
> >> int xc_domain_cacheflush(xc_interface *xch, uint32_t domid,
> >> xen_pfn_t start_pfn, xen_pfn_t nr_pfns)
> >> {
> >> +#if defined (__i386__) || defined (__x86_64__)
> >> + /*
> >> + * The x86 architecture provides cache coherency guarantees which prevent
> >> + * the need for this hypercall.
> >> + *
> >> + * This call however is made frequently during domain build and migrate
> >> + * for the benefit of ARM, where cache flushes are needed.
> >> + *
> >> + * Stub it out here on x86 as domctls take the global domctl lock in Xen
> >> + * which is detrimental to concurrent toolstack operations on other
> >> + * domains.
> >> + */
> >> + errno = ENOSYS;
> >> + return -1;
> >> +#else
> >> DECLARE_DOMCTL;
> >> domctl.cmd = XEN_DOMCTL_cacheflush;
> >> domctl.domain = (domid_t)domid;
> >> domctl.u.cacheflush.start_pfn = start_pfn;
> >> domctl.u.cacheflush.nr_pfns = nr_pfns;
> >> return do_domctl(xch, &domctl);
> >> +#endif
> >> }
> >>
> >> int xc_domain_pause(xc_interface *xch,
> >
>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-09-24 14:29 UTC | newest]
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2014-09-24 13:47 [PATCH for-4.5] tools/libxc: Avoid cacheflush toolstack hypercalls on x86 Andrew Cooper
2014-09-24 14:22 ` Ian Campbell
2014-09-24 14:24 ` Andrew Cooper
2014-09-24 14:29 ` Ian Campbell
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