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[RFC 1/8] memory: Allow eventfd add/del without starting a transaction
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From: |
Greg Kurz |
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Subject: |
[RFC 1/8] memory: Allow eventfd add/del without starting a transaction |
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Date: |
Thu, 25 Mar 2021 16:07:28 +0100 |
Each addition or deletion of an eventfd happens in its own MR
transaction. This doesn't scale well with multiqueue devices
that do 1:1 queue:vCPU mapping (e.g. virtio-scsi-pci or
virtio-blk-pci) : these devices typically create at least one
eventfd per queue and memory_region_transaction_commit(),
which is called during commit, also loops on eventfds, resulting
in a quadratic time complexity. This calls for batching : a
device should be able to add or delete its eventfds in a single
transaction.
Prepare ground for this by introducing extended versions of
memory_region_add_eventfd() and memory_region_del_eventfd()
that take an extra bool argument to control if a transaction
should be started or not.
No behavior change at this point.
Signed-off-by: Greg Kurz <groug@kaod.org>
---
include/exec/memory.h | 48 ++++++++++++++++++++++++++++++++-----------
softmmu/memory.c | 42 ++++++++++++++++++++++---------------
2 files changed, 62 insertions(+), 28 deletions(-)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 5728a681b27d..98ed552e001c 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -1848,13 +1848,25 @@ void memory_region_clear_flush_coalesced(MemoryRegion
*mr);
* @match_data: whether to match against @data, instead of just @addr
* @data: the data to match against the guest write
* @e: event notifier to be triggered when @addr, @size, and @data all match.
+ * @transaction: whether to start a transaction for the change
**/
-void memory_region_add_eventfd(MemoryRegion *mr,
- hwaddr addr,
- unsigned size,
- bool match_data,
- uint64_t data,
- EventNotifier *e);
+void memory_region_add_eventfd_full(MemoryRegion *mr,
+ hwaddr addr,
+ unsigned size,
+ bool match_data,
+ uint64_t data,
+ EventNotifier *e,
+ bool transaction);
+
+static inline void memory_region_add_eventfd(MemoryRegion *mr,
+ hwaddr addr,
+ unsigned size,
+ bool match_data,
+ uint64_t data,
+ EventNotifier *e)
+{
+ memory_region_add_eventfd_full(mr, addr, size, match_data, data, e, true);
+}
/**
* memory_region_del_eventfd: Cancel an eventfd.
@@ -1868,13 +1880,25 @@ void memory_region_add_eventfd(MemoryRegion *mr,
* @match_data: whether to match against @data, instead of just @addr
* @data: the data to match against the guest write
* @e: event notifier to be triggered when @addr, @size, and @data all match.
+ * @transaction: whether to start a transaction for the change
*/
-void memory_region_del_eventfd(MemoryRegion *mr,
- hwaddr addr,
- unsigned size,
- bool match_data,
- uint64_t data,
- EventNotifier *e);
+void memory_region_del_eventfd_full(MemoryRegion *mr,
+ hwaddr addr,
+ unsigned size,
+ bool match_data,
+ uint64_t data,
+ EventNotifier *e,
+ bool transaction);
+
+static inline void memory_region_del_eventfd(MemoryRegion *mr,
+ hwaddr addr,
+ unsigned size,
+ bool match_data,
+ uint64_t data,
+ EventNotifier *e)
+{
+ memory_region_del_eventfd_full(mr, addr, size, match_data, data, e, true);
+}
/**
* memory_region_add_subregion: Add a subregion to a container.
diff --git a/softmmu/memory.c b/softmmu/memory.c
index d4493ef9e430..1b1942d521cc 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2341,12 +2341,13 @@ void memory_region_clear_flush_coalesced(MemoryRegion
*mr)
static bool userspace_eventfd_warning;
-void memory_region_add_eventfd(MemoryRegion *mr,
- hwaddr addr,
- unsigned size,
- bool match_data,
- uint64_t data,
- EventNotifier *e)
+void memory_region_add_eventfd_full(MemoryRegion *mr,
+ hwaddr addr,
+ unsigned size,
+ bool match_data,
+ uint64_t data,
+ EventNotifier *e,
+ bool transaction)
{
MemoryRegionIoeventfd mrfd = {
.addr.start = int128_make64(addr),
@@ -2367,7 +2368,9 @@ void memory_region_add_eventfd(MemoryRegion *mr,
if (size) {
adjust_endianness(mr, &mrfd.data, size_memop(size) | MO_TE);
}
- memory_region_transaction_begin();
+ if (transaction) {
+ memory_region_transaction_begin();
+ }
for (i = 0; i < mr->ioeventfd_nb; ++i) {
if (memory_region_ioeventfd_before(&mrfd, &mr->ioeventfds[i])) {
break;
@@ -2380,15 +2383,18 @@ void memory_region_add_eventfd(MemoryRegion *mr,
sizeof(*mr->ioeventfds) * (mr->ioeventfd_nb-1 - i));
mr->ioeventfds[i] = mrfd;
ioeventfd_update_pending |= mr->enabled;
- memory_region_transaction_commit();
+ if (transaction) {
+ memory_region_transaction_commit();
+ }
}
-void memory_region_del_eventfd(MemoryRegion *mr,
- hwaddr addr,
- unsigned size,
- bool match_data,
- uint64_t data,
- EventNotifier *e)
+void memory_region_del_eventfd_full(MemoryRegion *mr,
+ hwaddr addr,
+ unsigned size,
+ bool match_data,
+ uint64_t data,
+ EventNotifier *e,
+ bool transaction)
{
MemoryRegionIoeventfd mrfd = {
.addr.start = int128_make64(addr),
@@ -2402,7 +2408,9 @@ void memory_region_del_eventfd(MemoryRegion *mr,
if (size) {
adjust_endianness(mr, &mrfd.data, size_memop(size) | MO_TE);
}
- memory_region_transaction_begin();
+ if (transaction) {
+ memory_region_transaction_begin();
+ }
for (i = 0; i < mr->ioeventfd_nb; ++i) {
if (memory_region_ioeventfd_equal(&mrfd, &mr->ioeventfds[i])) {
break;
@@ -2415,7 +2423,9 @@ void memory_region_del_eventfd(MemoryRegion *mr,
mr->ioeventfds = g_realloc(mr->ioeventfds,
sizeof(*mr->ioeventfds)*mr->ioeventfd_nb +
1);
ioeventfd_update_pending |= mr->enabled;
- memory_region_transaction_commit();
+ if (transaction) {
+ memory_region_transaction_commit();
+ }
}
static void memory_region_update_container_subregions(MemoryRegion *subregion)
--
2.26.3