Re: [PATCH] kvmtool: Add parameter to specifiy number of threads in thread_pool
On Mon, Jun 29, 2015 at 10:45:03AM +0100, Will Deacon wrote:
> On Mon, Jun 29, 2015 at 08:45:44AM +0100, Andreas Herrmann wrote:
> >
> > With current code the number of threads added to the thread_pool
> > equals number of online CPUs. Thus on an OcteonIII cn78xx system we
> > usually have 48 threads per guest just for the thread_pool. IMHO this
> > is overkill for guests that just have a few vCPUs and/or if a guest is
> > pinned to a subset of host CPUs. E.g.
> >
> > # numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 -k paravirt -d rootfs.ext3 ...
> > # ps -La | grep threadpool-work | wc -l
> > 48
> >
> > Don't change default behaviour (for sake of compatibility) but
> > introduce a new parameter ("-t" or "--threads") that allows to specify
> > number of threads to be created for the thread_pool:
> >
> > # numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 --threads 4 -k paravirt -d ...
> > # ps -La | grep threadpool-work | wc -l
> > 4
>
> We should probably bound this on some minimum value. I assume things go
> pear-shaped if you pass --threads 1 (or 0, or -1)?
Ouch, yes, range must be checked (esp. for -1).
I think the passed value should be in [1, number of online CPUs].
Andreas
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Re: [PATCH] kvmtool: Add parameter to specifiy number of threads in thread_pool
On Mon, Jun 29, 2015 at 08:45:44AM +0100, Andreas Herrmann wrote:
>
> With current code the number of threads added to the thread_pool
> equals number of online CPUs. Thus on an OcteonIII cn78xx system we
> usually have 48 threads per guest just for the thread_pool. IMHO this
> is overkill for guests that just have a few vCPUs and/or if a guest is
> pinned to a subset of host CPUs. E.g.
>
> # numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 -k paravirt -d rootfs.ext3 ...
> # ps -La | grep threadpool-work | wc -l
> 48
>
> Don't change default behaviour (for sake of compatibility) but
> introduce a new parameter ("-t" or "--threads") that allows to specify
> number of threads to be created for the thread_pool:
>
> # numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 --threads 4 -k paravirt -d ...
> # ps -La | grep threadpool-work | wc -l
> 4
We should probably bound this on some minimum value. I assume things go
pear-shaped if you pass --threads 1 (or 0, or -1)?
Will
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[PATCH] kvmtool: Add parameter to specifiy number of threads in thread_pool
With current code the number of threads added to the thread_pool
equals number of online CPUs. Thus on an OcteonIII cn78xx system we
usually have 48 threads per guest just for the thread_pool. IMHO this
is overkill for guests that just have a few vCPUs and/or if a guest is
pinned to a subset of host CPUs. E.g.
# numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 -k paravirt -d rootfs.ext3 ...
# ps -La | grep threadpool-work | wc -l
48
Don't change default behaviour (for sake of compatibility) but
introduce a new parameter ("-t" or "--threads") that allows to specify
number of threads to be created for the thread_pool:
# numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 --threads 4 -k paravirt -d ...
# ps -La | grep threadpool-work | wc -l
4
Signed-off-by: Andreas Herrmann
---
builtin-run.c|2 ++
include/kvm/kvm-config.h |1 +
util/threadpool.c|5 -
3 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/builtin-run.c b/builtin-run.c
index 1ee75ad..86de53d 100644
--- a/builtin-run.c
+++ b/builtin-run.c
@@ -131,6 +131,8 @@ void kvm_run_set_wrapper_sandbox(void)
" rootfs"), \
OPT_STRING('\0', "hugetlbfs", &(cfg)->hugetlbfs_path, "path", \
"Hugetlbfs path"), \
+ OPT_INTEGER('t', "threads", &(cfg)->nrthreads, \
+"Number of threads in thread_pool"), \
\
OPT_GROUP("Kernel options:"), \
OPT_STRING('k', "kernel", &(cfg)->kernel_filename, "kernel",\
diff --git a/include/kvm/kvm-config.h b/include/kvm/kvm-config.h
index 386fa8c..9cc50f5 100644
--- a/include/kvm/kvm-config.h
+++ b/include/kvm/kvm-config.h
@@ -27,6 +27,7 @@ struct kvm_config {
int active_console;
int debug_iodelay;
int nrcpus;
+ int nrthreads;
const char *kernel_cmdline;
const char *kernel_filename;
const char *vmlinux_filename;
diff --git a/util/threadpool.c b/util/threadpool.c
index e64aa26..620fdbd 100644
--- a/util/threadpool.c
+++ b/util/threadpool.c
@@ -124,7 +124,10 @@ static int thread_pool__addthread(void)
int thread_pool__init(struct kvm *kvm)
{
unsigned long i;
- unsigned int thread_count = sysconf(_SC_NPROCESSORS_ONLN);
+ unsigned int thread_count;
+
+ thread_count = kvm->cfg.nrthreads ? kvm->cfg.nrthreads :
+ sysconf(_SC_NPROCESSORS_ONLN);
running = true;
--
1.7.9.5
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[PATCH] kvmtool: Add parameter to specifiy number of threads in thread_pool
With current code the number of threads added to the thread_pool
equals number of online CPUs. IMHO on systems with many CPUs this is
overkill for guests that just have a few vCPUs and/or if a guest is
pinned to a subset of host CPUs. E.g. of a system with 48 cores
# numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 -k paravirt -d rootfs.ext3 ...
# ps -La | grep threadpool-work | wc -l
48
Don't change default behaviour (for sake of compatibility) but
introduce a new parameter ("-t" or "--threads") that allows to specify
number of threads to be created for the thread_pool:
# numactl -C 4,5,7,8 ./lkvm run -c 2 -m 256 --threads 4 -k paravirt -d ...
# ps -La | grep threadpool-work | wc -l
4
Signed-off-by: Andreas Herrmann
---
tools/kvm/builtin-run.c|2 ++
tools/kvm/include/kvm/kvm-config.h |1 +
tools/kvm/util/threadpool.c|5 -
3 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/tools/kvm/builtin-run.c b/tools/kvm/builtin-run.c
index 1ee75ad..86de53d 100644
--- a/tools/kvm/builtin-run.c
+++ b/tools/kvm/builtin-run.c
@@ -131,6 +131,8 @@ void kvm_run_set_wrapper_sandbox(void)
" rootfs"), \
OPT_STRING('\0', "hugetlbfs", &(cfg)->hugetlbfs_path, "path", \
"Hugetlbfs path"), \
+ OPT_INTEGER('t', "threads", &(cfg)->nrthreads, \
+"Number of threads in thread_pool"), \
\
OPT_GROUP("Kernel options:"), \
OPT_STRING('k', "kernel", &(cfg)->kernel_filename, "kernel",\
diff --git a/tools/kvm/include/kvm/kvm-config.h
b/tools/kvm/include/kvm/kvm-config.h
index 386fa8c..9cc50f5 100644
--- a/tools/kvm/include/kvm/kvm-config.h
+++ b/tools/kvm/include/kvm/kvm-config.h
@@ -27,6 +27,7 @@ struct kvm_config {
int active_console;
int debug_iodelay;
int nrcpus;
+ int nrthreads;
const char *kernel_cmdline;
const char *kernel_filename;
const char *vmlinux_filename;
diff --git a/tools/kvm/util/threadpool.c b/tools/kvm/util/threadpool.c
index e64aa26..620fdbd 100644
--- a/tools/kvm/util/threadpool.c
+++ b/tools/kvm/util/threadpool.c
@@ -124,7 +124,10 @@ static int thread_pool__addthread(void)
int thread_pool__init(struct kvm *kvm)
{
unsigned long i;
- unsigned int thread_count = sysconf(_SC_NPROCESSORS_ONLN);
+ unsigned int thread_count;
+
+ thread_count = kvm->cfg.nrthreads ? kvm->cfg.nrthreads :
+ sysconf(_SC_NPROCESSORS_ONLN);
running = true;
--
1.7.9.5
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