* [PATCH v4 0/2] KVM: s390: add counters for vsie performance
@ 2023-10-09 9:32 Nico Boehr
2023-10-09 9:32 ` [PATCH v4 1/2] KVM: s390: add stat counter for shadow gmap events Nico Boehr
2023-10-09 9:32 ` [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier Nico Boehr
0 siblings, 2 replies; 7+ messages in thread
From: Nico Boehr @ 2023-10-09 9:32 UTC (permalink / raw)
To: borntraeger, frankja, imbrenda, david; +Cc: kvm, linux-s390
v4:
---
* fix indent in tracepoint (thanks Janosch)
v3:
---
* rename te -> entry (David)
* add counters for gmap reuse and gmap create (David)
v2:
---
* also count shadowing of pages (Janosch)
* fix naming of counters (Janosch)
* mention shadowing of multiple levels is counted in each level (Claudio)
* fix inaccuate commit description regarding gmap notifier (Claudio)
When running a guest-3 via VSIE, guest-1 needs to shadow the page table
structures of guest-2.
To reflect changes of the guest-2 in the _shadowed_ page table structures,
the _shadowing_ sturctures sometimes need to be rebuilt. Since this is a
costly operation, it should be avoided whenever possible.
This series adds kvm stat counters to count the number of shadow gmaps
created and a tracepoint whenever something is unshadowed. This is a first
step to try and improve VSIE performance.
Please note that "KVM: s390: add tracepoint in gmap notifier" has some
checkpatch --strict findings. I did not fix these since the tracepoint
definition would then look completely different from all the other
tracepoints in arch/s390/kvm/trace-s390.h. If you want me to fix that,
please let me know.
Nico Boehr (2):
KVM: s390: add stat counter for shadow gmap events
KVM: s390: add tracepoint in gmap notifier
arch/s390/include/asm/kvm_host.h | 7 +++++++
arch/s390/kvm/gaccess.c | 7 +++++++
arch/s390/kvm/kvm-s390.c | 11 ++++++++++-
arch/s390/kvm/trace-s390.h | 23 +++++++++++++++++++++++
arch/s390/kvm/vsie.c | 5 ++++-
5 files changed, 51 insertions(+), 2 deletions(-)
--
2.41.0
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v4 1/2] KVM: s390: add stat counter for shadow gmap events
2023-10-09 9:32 [PATCH v4 0/2] KVM: s390: add counters for vsie performance Nico Boehr
@ 2023-10-09 9:32 ` Nico Boehr
2023-10-09 13:20 ` Claudio Imbrenda
2023-10-09 13:31 ` Janosch Frank
2023-10-09 9:32 ` [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier Nico Boehr
1 sibling, 2 replies; 7+ messages in thread
From: Nico Boehr @ 2023-10-09 9:32 UTC (permalink / raw)
To: borntraeger, frankja, imbrenda, david; +Cc: kvm, linux-s390
The shadow gmap tracks memory of nested guests (guest-3). In certain
scenarios, the shadow gmap needs to be rebuilt, which is a costly operation
since it involves a SIE exit into guest-1 for every entry in the respective
shadow level.
Add kvm stat counters when new shadow structures are created at various
levels. Also add a counter gmap_shadow_create when a completely fresh
shadow gmap is created as well as a counter gmap_shadow_reuse when an
existing gmap is being reused.
Note that when several levels are shadowed at once, counters on all
affected levels will be increased.
Also note that not all page table levels need to be present and a ASCE
can directly point to e.g. a segment table. In this case, a new segment
table will always be equivalent to a new shadow gmap and hence will be
counted as gmap_shadow_create and not as gmap_shadow_segment.
Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
arch/s390/include/asm/kvm_host.h | 7 +++++++
arch/s390/kvm/gaccess.c | 7 +++++++
arch/s390/kvm/kvm-s390.c | 9 ++++++++-
arch/s390/kvm/vsie.c | 5 ++++-
4 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 427f9528a7b6..67a298b6cf6e 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -777,6 +777,13 @@ struct kvm_vm_stat {
u64 inject_service_signal;
u64 inject_virtio;
u64 aen_forward;
+ u64 gmap_shadow_create;
+ u64 gmap_shadow_reuse;
+ u64 gmap_shadow_r1_entry;
+ u64 gmap_shadow_r2_entry;
+ u64 gmap_shadow_r3_entry;
+ u64 gmap_shadow_sg_entry;
+ u64 gmap_shadow_pg_entry;
};
struct kvm_arch_memory_slot {
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 6d6bc19b37dc..ff8349d17b33 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1382,6 +1382,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
unsigned long *pgt, int *dat_protection,
int *fake)
{
+ struct kvm *kvm;
struct gmap *parent;
union asce asce;
union vaddress vaddr;
@@ -1390,6 +1391,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
*fake = 0;
*dat_protection = 0;
+ kvm = sg->private;
parent = sg->parent;
vaddr.addr = saddr;
asce.val = sg->orig_asce;
@@ -1450,6 +1452,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
rc = gmap_shadow_r2t(sg, saddr, rfte.val, *fake);
if (rc)
return rc;
+ kvm->stat.gmap_shadow_r1_entry++;
}
fallthrough;
case ASCE_TYPE_REGION2: {
@@ -1478,6 +1481,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
rc = gmap_shadow_r3t(sg, saddr, rste.val, *fake);
if (rc)
return rc;
+ kvm->stat.gmap_shadow_r2_entry++;
}
fallthrough;
case ASCE_TYPE_REGION3: {
@@ -1515,6 +1519,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
rc = gmap_shadow_sgt(sg, saddr, rtte.val, *fake);
if (rc)
return rc;
+ kvm->stat.gmap_shadow_r3_entry++;
}
fallthrough;
case ASCE_TYPE_SEGMENT: {
@@ -1548,6 +1553,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
rc = gmap_shadow_pgt(sg, saddr, ste.val, *fake);
if (rc)
return rc;
+ kvm->stat.gmap_shadow_sg_entry++;
}
}
/* Return the parent address of the page table */
@@ -1618,6 +1624,7 @@ int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg,
pte.p |= dat_protection;
if (!rc)
rc = gmap_shadow_page(sg, saddr, __pte(pte.val));
+ vcpu->kvm->stat.gmap_shadow_pg_entry++;
ipte_unlock(vcpu->kvm);
mmap_read_unlock(sg->mm);
return rc;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index b3f17e014cab..b42493110d76 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -66,7 +66,14 @@ const struct _kvm_stats_desc kvm_vm_stats_desc[] = {
STATS_DESC_COUNTER(VM, inject_pfault_done),
STATS_DESC_COUNTER(VM, inject_service_signal),
STATS_DESC_COUNTER(VM, inject_virtio),
- STATS_DESC_COUNTER(VM, aen_forward)
+ STATS_DESC_COUNTER(VM, aen_forward),
+ STATS_DESC_COUNTER(VM, gmap_shadow_reuse),
+ STATS_DESC_COUNTER(VM, gmap_shadow_create),
+ STATS_DESC_COUNTER(VM, gmap_shadow_r1_entry),
+ STATS_DESC_COUNTER(VM, gmap_shadow_r2_entry),
+ STATS_DESC_COUNTER(VM, gmap_shadow_r3_entry),
+ STATS_DESC_COUNTER(VM, gmap_shadow_sg_entry),
+ STATS_DESC_COUNTER(VM, gmap_shadow_pg_entry),
};
const struct kvm_stats_header kvm_vm_stats_header = {
diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
index 61499293c2ac..02dcbe82a8e5 100644
--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -1214,8 +1214,10 @@ static int acquire_gmap_shadow(struct kvm_vcpu *vcpu,
* we're holding has been unshadowed. If the gmap is still valid,
* we can safely reuse it.
*/
- if (vsie_page->gmap && gmap_shadow_valid(vsie_page->gmap, asce, edat))
+ if (vsie_page->gmap && gmap_shadow_valid(vsie_page->gmap, asce, edat)) {
+ vcpu->kvm->stat.gmap_shadow_reuse++;
return 0;
+ }
/* release the old shadow - if any, and mark the prefix as unmapped */
release_gmap_shadow(vsie_page);
@@ -1223,6 +1225,7 @@ static int acquire_gmap_shadow(struct kvm_vcpu *vcpu,
if (IS_ERR(gmap))
return PTR_ERR(gmap);
gmap->private = vcpu->kvm;
+ vcpu->kvm->stat.gmap_shadow_create++;
WRITE_ONCE(vsie_page->gmap, gmap);
return 0;
}
--
2.41.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier
2023-10-09 9:32 [PATCH v4 0/2] KVM: s390: add counters for vsie performance Nico Boehr
2023-10-09 9:32 ` [PATCH v4 1/2] KVM: s390: add stat counter for shadow gmap events Nico Boehr
@ 2023-10-09 9:32 ` Nico Boehr
2023-10-09 13:20 ` Claudio Imbrenda
2023-10-09 13:32 ` Janosch Frank
1 sibling, 2 replies; 7+ messages in thread
From: Nico Boehr @ 2023-10-09 9:32 UTC (permalink / raw)
To: borntraeger, frankja, imbrenda, david; +Cc: kvm, linux-s390
The gmap notifier is called for changes in table entries with the
notifier bit set. To diagnose performance issues, it can be useful to
see what causes certain changes in the gmap.
Hence, add a tracepoint in the gmap notifier.
Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
---
arch/s390/kvm/kvm-s390.c | 2 ++
arch/s390/kvm/trace-s390.h | 23 +++++++++++++++++++++++
2 files changed, 25 insertions(+)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index b42493110d76..11676b81e6bf 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4060,6 +4060,8 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
unsigned long prefix;
unsigned long i;
+ trace_kvm_s390_gmap_notifier(start, end, gmap_is_shadow(gmap));
+
if (gmap_is_shadow(gmap))
return;
if (start >= 1UL << 31)
diff --git a/arch/s390/kvm/trace-s390.h b/arch/s390/kvm/trace-s390.h
index 6f0209d45164..9ac92dbf680d 100644
--- a/arch/s390/kvm/trace-s390.h
+++ b/arch/s390/kvm/trace-s390.h
@@ -333,6 +333,29 @@ TRACE_EVENT(kvm_s390_airq_suppressed,
__entry->id, __entry->isc)
);
+/*
+ * Trace point for gmap notifier calls.
+ */
+TRACE_EVENT(kvm_s390_gmap_notifier,
+ TP_PROTO(unsigned long start, unsigned long end, unsigned int shadow),
+ TP_ARGS(start, end, shadow),
+
+ TP_STRUCT__entry(
+ __field(unsigned long, start)
+ __field(unsigned long, end)
+ __field(unsigned int, shadow)
+ ),
+
+ TP_fast_assign(
+ __entry->start = start;
+ __entry->end = end;
+ __entry->shadow = shadow;
+ ),
+
+ TP_printk("gmap notified (start:0x%lx end:0x%lx shadow:%d)",
+ __entry->start, __entry->end, __entry->shadow)
+ );
+
#endif /* _TRACE_KVMS390_H */
--
2.41.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v4 1/2] KVM: s390: add stat counter for shadow gmap events
2023-10-09 9:32 ` [PATCH v4 1/2] KVM: s390: add stat counter for shadow gmap events Nico Boehr
@ 2023-10-09 13:20 ` Claudio Imbrenda
2023-10-09 13:31 ` Janosch Frank
1 sibling, 0 replies; 7+ messages in thread
From: Claudio Imbrenda @ 2023-10-09 13:20 UTC (permalink / raw)
To: Nico Boehr; +Cc: borntraeger, frankja, david, kvm, linux-s390
On Mon, 9 Oct 2023 11:32:52 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:
> The shadow gmap tracks memory of nested guests (guest-3). In certain
> scenarios, the shadow gmap needs to be rebuilt, which is a costly operation
> since it involves a SIE exit into guest-1 for every entry in the respective
> shadow level.
>
> Add kvm stat counters when new shadow structures are created at various
> levels. Also add a counter gmap_shadow_create when a completely fresh
> shadow gmap is created as well as a counter gmap_shadow_reuse when an
> existing gmap is being reused.
>
> Note that when several levels are shadowed at once, counters on all
> affected levels will be increased.
>
> Also note that not all page table levels need to be present and a ASCE
> can directly point to e.g. a segment table. In this case, a new segment
> table will always be equivalent to a new shadow gmap and hence will be
> counted as gmap_shadow_create and not as gmap_shadow_segment.
>
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
> arch/s390/include/asm/kvm_host.h | 7 +++++++
> arch/s390/kvm/gaccess.c | 7 +++++++
> arch/s390/kvm/kvm-s390.c | 9 ++++++++-
> arch/s390/kvm/vsie.c | 5 ++++-
> 4 files changed, 26 insertions(+), 2 deletions(-)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 427f9528a7b6..67a298b6cf6e 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -777,6 +777,13 @@ struct kvm_vm_stat {
> u64 inject_service_signal;
> u64 inject_virtio;
> u64 aen_forward;
> + u64 gmap_shadow_create;
> + u64 gmap_shadow_reuse;
> + u64 gmap_shadow_r1_entry;
> + u64 gmap_shadow_r2_entry;
> + u64 gmap_shadow_r3_entry;
> + u64 gmap_shadow_sg_entry;
> + u64 gmap_shadow_pg_entry;
> };
>
> struct kvm_arch_memory_slot {
> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
> index 6d6bc19b37dc..ff8349d17b33 100644
> --- a/arch/s390/kvm/gaccess.c
> +++ b/arch/s390/kvm/gaccess.c
> @@ -1382,6 +1382,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
> unsigned long *pgt, int *dat_protection,
> int *fake)
> {
> + struct kvm *kvm;
> struct gmap *parent;
> union asce asce;
> union vaddress vaddr;
> @@ -1390,6 +1391,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
>
> *fake = 0;
> *dat_protection = 0;
> + kvm = sg->private;
> parent = sg->parent;
> vaddr.addr = saddr;
> asce.val = sg->orig_asce;
> @@ -1450,6 +1452,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
> rc = gmap_shadow_r2t(sg, saddr, rfte.val, *fake);
> if (rc)
> return rc;
> + kvm->stat.gmap_shadow_r1_entry++;
> }
> fallthrough;
> case ASCE_TYPE_REGION2: {
> @@ -1478,6 +1481,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
> rc = gmap_shadow_r3t(sg, saddr, rste.val, *fake);
> if (rc)
> return rc;
> + kvm->stat.gmap_shadow_r2_entry++;
> }
> fallthrough;
> case ASCE_TYPE_REGION3: {
> @@ -1515,6 +1519,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
> rc = gmap_shadow_sgt(sg, saddr, rtte.val, *fake);
> if (rc)
> return rc;
> + kvm->stat.gmap_shadow_r3_entry++;
> }
> fallthrough;
> case ASCE_TYPE_SEGMENT: {
> @@ -1548,6 +1553,7 @@ static int kvm_s390_shadow_tables(struct gmap *sg, unsigned long saddr,
> rc = gmap_shadow_pgt(sg, saddr, ste.val, *fake);
> if (rc)
> return rc;
> + kvm->stat.gmap_shadow_sg_entry++;
> }
> }
> /* Return the parent address of the page table */
> @@ -1618,6 +1624,7 @@ int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg,
> pte.p |= dat_protection;
> if (!rc)
> rc = gmap_shadow_page(sg, saddr, __pte(pte.val));
> + vcpu->kvm->stat.gmap_shadow_pg_entry++;
> ipte_unlock(vcpu->kvm);
> mmap_read_unlock(sg->mm);
> return rc;
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index b3f17e014cab..b42493110d76 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -66,7 +66,14 @@ const struct _kvm_stats_desc kvm_vm_stats_desc[] = {
> STATS_DESC_COUNTER(VM, inject_pfault_done),
> STATS_DESC_COUNTER(VM, inject_service_signal),
> STATS_DESC_COUNTER(VM, inject_virtio),
> - STATS_DESC_COUNTER(VM, aen_forward)
> + STATS_DESC_COUNTER(VM, aen_forward),
> + STATS_DESC_COUNTER(VM, gmap_shadow_reuse),
> + STATS_DESC_COUNTER(VM, gmap_shadow_create),
> + STATS_DESC_COUNTER(VM, gmap_shadow_r1_entry),
> + STATS_DESC_COUNTER(VM, gmap_shadow_r2_entry),
> + STATS_DESC_COUNTER(VM, gmap_shadow_r3_entry),
> + STATS_DESC_COUNTER(VM, gmap_shadow_sg_entry),
> + STATS_DESC_COUNTER(VM, gmap_shadow_pg_entry),
> };
>
> const struct kvm_stats_header kvm_vm_stats_header = {
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 61499293c2ac..02dcbe82a8e5 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -1214,8 +1214,10 @@ static int acquire_gmap_shadow(struct kvm_vcpu *vcpu,
> * we're holding has been unshadowed. If the gmap is still valid,
> * we can safely reuse it.
> */
> - if (vsie_page->gmap && gmap_shadow_valid(vsie_page->gmap, asce, edat))
> + if (vsie_page->gmap && gmap_shadow_valid(vsie_page->gmap, asce, edat)) {
> + vcpu->kvm->stat.gmap_shadow_reuse++;
> return 0;
> + }
>
> /* release the old shadow - if any, and mark the prefix as unmapped */
> release_gmap_shadow(vsie_page);
> @@ -1223,6 +1225,7 @@ static int acquire_gmap_shadow(struct kvm_vcpu *vcpu,
> if (IS_ERR(gmap))
> return PTR_ERR(gmap);
> gmap->private = vcpu->kvm;
> + vcpu->kvm->stat.gmap_shadow_create++;
> WRITE_ONCE(vsie_page->gmap, gmap);
> return 0;
> }
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier
2023-10-09 9:32 ` [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier Nico Boehr
@ 2023-10-09 13:20 ` Claudio Imbrenda
2023-10-09 13:32 ` Janosch Frank
1 sibling, 0 replies; 7+ messages in thread
From: Claudio Imbrenda @ 2023-10-09 13:20 UTC (permalink / raw)
To: Nico Boehr; +Cc: borntraeger, frankja, david, kvm, linux-s390
On Mon, 9 Oct 2023 11:32:53 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:
> The gmap notifier is called for changes in table entries with the
> notifier bit set. To diagnose performance issues, it can be useful to
> see what causes certain changes in the gmap.
>
> Hence, add a tracepoint in the gmap notifier.
>
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
> arch/s390/kvm/kvm-s390.c | 2 ++
> arch/s390/kvm/trace-s390.h | 23 +++++++++++++++++++++++
> 2 files changed, 25 insertions(+)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index b42493110d76..11676b81e6bf 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -4060,6 +4060,8 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
> unsigned long prefix;
> unsigned long i;
>
> + trace_kvm_s390_gmap_notifier(start, end, gmap_is_shadow(gmap));
> +
> if (gmap_is_shadow(gmap))
> return;
> if (start >= 1UL << 31)
> diff --git a/arch/s390/kvm/trace-s390.h b/arch/s390/kvm/trace-s390.h
> index 6f0209d45164..9ac92dbf680d 100644
> --- a/arch/s390/kvm/trace-s390.h
> +++ b/arch/s390/kvm/trace-s390.h
> @@ -333,6 +333,29 @@ TRACE_EVENT(kvm_s390_airq_suppressed,
> __entry->id, __entry->isc)
> );
>
> +/*
> + * Trace point for gmap notifier calls.
> + */
> +TRACE_EVENT(kvm_s390_gmap_notifier,
> + TP_PROTO(unsigned long start, unsigned long end, unsigned int shadow),
> + TP_ARGS(start, end, shadow),
> +
> + TP_STRUCT__entry(
> + __field(unsigned long, start)
> + __field(unsigned long, end)
> + __field(unsigned int, shadow)
> + ),
> +
> + TP_fast_assign(
> + __entry->start = start;
> + __entry->end = end;
> + __entry->shadow = shadow;
> + ),
> +
> + TP_printk("gmap notified (start:0x%lx end:0x%lx shadow:%d)",
> + __entry->start, __entry->end, __entry->shadow)
> + );
> +
>
> #endif /* _TRACE_KVMS390_H */
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v4 1/2] KVM: s390: add stat counter for shadow gmap events
2023-10-09 9:32 ` [PATCH v4 1/2] KVM: s390: add stat counter for shadow gmap events Nico Boehr
2023-10-09 13:20 ` Claudio Imbrenda
@ 2023-10-09 13:31 ` Janosch Frank
1 sibling, 0 replies; 7+ messages in thread
From: Janosch Frank @ 2023-10-09 13:31 UTC (permalink / raw)
To: Nico Boehr, borntraeger, imbrenda, david; +Cc: kvm, linux-s390
On 10/9/23 11:32, Nico Boehr wrote:
> The shadow gmap tracks memory of nested guests (guest-3). In certain
> scenarios, the shadow gmap needs to be rebuilt, which is a costly operation
> since it involves a SIE exit into guest-1 for every entry in the respective
> shadow level.
>
> Add kvm stat counters when new shadow structures are created at various
> levels. Also add a counter gmap_shadow_create when a completely fresh
> shadow gmap is created as well as a counter gmap_shadow_reuse when an
> existing gmap is being reused.
>
> Note that when several levels are shadowed at once, counters on all
> affected levels will be increased.
>
> Also note that not all page table levels need to be present and a ASCE
> can directly point to e.g. a segment table. In this case, a new segment
> table will always be equivalent to a new shadow gmap and hence will be
> counted as gmap_shadow_create and not as gmap_shadow_segment.
>
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier
2023-10-09 9:32 ` [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier Nico Boehr
2023-10-09 13:20 ` Claudio Imbrenda
@ 2023-10-09 13:32 ` Janosch Frank
1 sibling, 0 replies; 7+ messages in thread
From: Janosch Frank @ 2023-10-09 13:32 UTC (permalink / raw)
To: Nico Boehr, borntraeger, imbrenda, david; +Cc: kvm, linux-s390
On 10/9/23 11:32, Nico Boehr wrote:
> The gmap notifier is called for changes in table entries with the
> notifier bit set. To diagnose performance issues, it can be useful to
> see what causes certain changes in the gmap.
>
> Hence, add a tracepoint in the gmap notifier.
>
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2023-10-09 13:38 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-10-09 9:32 [PATCH v4 0/2] KVM: s390: add counters for vsie performance Nico Boehr
2023-10-09 9:32 ` [PATCH v4 1/2] KVM: s390: add stat counter for shadow gmap events Nico Boehr
2023-10-09 13:20 ` Claudio Imbrenda
2023-10-09 13:31 ` Janosch Frank
2023-10-09 9:32 ` [PATCH v4 2/2] KVM: s390: add tracepoint in gmap notifier Nico Boehr
2023-10-09 13:20 ` Claudio Imbrenda
2023-10-09 13:32 ` Janosch Frank
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