Re: [PATCH v1] softmmu/vl: make default prealloc-threads work w/o -mem-prealloc
On Thu, 11 Mar 2021 11:59:18 +0300
Denis Plotnikov wrote:
> Preallocation in memory backends can be specified with either global
> QEMU option "-mem-prealloc", or with per-backend property
> "prealloc=true". In the latter case, however, the default for the
> number of preallocation threads is not set to the number of vcpus, but
> remains at 1 instead.
>
> Fix it by setting the "prealloc-threads" sugar property of
> "memory-backend" to the number of vcpus unconditionally.
well, number of prealloc-threads are policy that should be set by user.
it was kept equal to vcpus for compat reasons with "-mem-prealloc",
for if one goes with supplying memory backends explicitly, one is supposed
to set prealloc-threads explicitly as well if default(==1) doesn't
suit user. It could be equal to #vcpus or be a different numbers
depending on host CPU configuration. That was intent when
commit ffac16fab3 was introduced.
Imagine one has a VM with a lot of VCPUs but not so much of of RAM,
setting prealloc-threads to #VCPUs will be wasting CPU resources
at least.
> Fixes: ffac16fab3 ("hostmem: introduce "prealloc-threads" property")
>
> Signed-off-by: Denis Plotnikov
> ---
> softmmu/vl.c | 17 ++---
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index ff488ea3e7db..e392e226a2d3 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -2300,14 +2300,17 @@ static void qemu_validate_options(void)
>
> static void qemu_process_sugar_options(void)
> {
> -if (mem_prealloc) {
> -char *val;
> +char *val;
>
> -val = g_strdup_printf("%d",
> - (uint32_t)
> qemu_opt_get_number(qemu_find_opts_singleton("smp-opts"), "cpus", 1));
> -object_register_sugar_prop("memory-backend", "prealloc-threads", val,
> - false);
> -g_free(val);
> +val = g_strdup_printf("%d",
> + (uint32_t) qemu_opt_get_number(
> + qemu_find_opts_singleton("smp-opts"), "cpus",
> 1));
> +
> +object_register_sugar_prop("memory-backend", "prealloc-threads", val,
> +false);
> +g_free(val);
> +
> +if (mem_prealloc) {
> object_register_sugar_prop("memory-backend", "prealloc", "on",
> false);
> }
>
Re: [PATCH v1] softmmu/vl: make default prealloc-threads work w/o -mem-prealloc
On 11/03/21 09:59, Denis Plotnikov wrote:
diff --git a/softmmu/vl.c b/softmmu/vl.c
index ff488ea3e7db..e392e226a2d3 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2300,14 +2300,17 @@ static void qemu_validate_options(void)
static void qemu_process_sugar_options(void)
{
-if (mem_prealloc) {
-char *val;
+char *val;
-val = g_strdup_printf("%d",
- (uint32_t) qemu_opt_get_number(qemu_find_opts_singleton("smp-opts"),
"cpus", 1));
-object_register_sugar_prop("memory-backend", "prealloc-threads", val,
- false);
-g_free(val);
+val = g_strdup_printf("%d",
+ (uint32_t) qemu_opt_get_number(
+ qemu_find_opts_singleton("smp-opts"), "cpus", 1));
+
+object_register_sugar_prop("memory-backend", "prealloc-threads", val,
+false);
+g_free(val);
+
+if (mem_prealloc) {
object_register_sugar_prop("memory-backend", "prealloc", "on", false);
}
Hi Denis, this patch breaks make check-qtest-arm:
G_TEST_DBUS_DAEMON=/home/pbonzini/work/upstream/qemu/tests/dbus-vmstate-daemon.sh
QTEST_QEMU_IMG=./qemu-img MALLOC_PERTURB_=45
QTEST_QEMU_BINARY=./qemu-system-arm
/home/pbonzini/work/upstream/qemu/+bb/tests/qtest/npcm7xx_emc-test --tap -k
# random seed: R02Sac2b21edc4fb48abab9f9723147ddbd5
1..6
# Start of arm tests
# Start of npcm7xx_emc tests
# Start of emc[0] tests
# starting QEMU: exec ./qemu-system-arm -qtest unix:/tmp/qtest-839596.sock
-qtest-log /dev/null -chardev socket,path=/tmp/qtest-839596.qmp,id=char0 -mon
chardev=char0,mode=control -display none -machine quanta-gsj -accel qtest
qemu-system-arm: Invalid SMP CPUs 1. The min CPUs supported by machine
'quanta-gsj' is 2
Paolo
Re: [PATCH v1] softmmu/vl: make default prealloc-threads work w/o -mem-prealloc
On 11/03/21 09:59, Denis Plotnikov wrote:
Preallocation in memory backends can be specified with either global
QEMU option "-mem-prealloc", or with per-backend property
"prealloc=true". In the latter case, however, the default for the
number of preallocation threads is not set to the number of vcpus, but
remains at 1 instead.
Fix it by setting the "prealloc-threads" sugar property of
"memory-backend" to the number of vcpus unconditionally.
Fixes: ffac16fab3 ("hostmem: introduce "prealloc-threads" property")
Signed-off-by: Denis Plotnikov
---
softmmu/vl.c | 17 ++---
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/softmmu/vl.c b/softmmu/vl.c
index ff488ea3e7db..e392e226a2d3 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2300,14 +2300,17 @@ static void qemu_validate_options(void)
static void qemu_process_sugar_options(void)
{
-if (mem_prealloc) {
-char *val;
+char *val;
-val = g_strdup_printf("%d",
- (uint32_t) qemu_opt_get_number(qemu_find_opts_singleton("smp-opts"),
"cpus", 1));
-object_register_sugar_prop("memory-backend", "prealloc-threads", val,
- false);
-g_free(val);
+val = g_strdup_printf("%d",
+ (uint32_t) qemu_opt_get_number(
+ qemu_find_opts_singleton("smp-opts"), "cpus", 1));
+
+object_register_sugar_prop("memory-backend", "prealloc-threads", val,
+false);
+g_free(val);
+
+if (mem_prealloc) {
object_register_sugar_prop("memory-backend", "prealloc", "on", false);
}
Queued, thanks.
Paolo
