With current code the number of threads added to the thread_pool
equals number of online CPUs. So on cn78xx 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 <andreas.herrmann@xxxxxxxxxxxxxxxxxx>
---
builtin-run.c | 6 ++++++
include/kvm/kvm-config.h | 1 +
util/threadpool.c | 2 +-
3 files changed, 8 insertions(+), 1 deletion(-)
New in v2: paramter must be in range [1, number of online cpus]
otherwise the default (number of online cpus) will be used.
Andreas
diff --git a/builtin-run.c b/builtin-run.c
index 1ee75ad..40ab9c6 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", \
@@ -590,6 +592,10 @@ static struct kvm *kvm_cmd_run_init(int argc, const char **argv)
if (!kvm->cfg.network)
kvm->cfg.network = DEFAULT_NETWORK;
+ if (!kvm->cfg.nrthreads || (kvm->cfg.nrthreads < 0) ||
+ ((unsigned int) kvm->cfg.nrthreads > nr_online_cpus))
+ kvm->cfg.nrthreads = nr_online_cpus;
+
memset(real_cmdline, 0, sizeof(real_cmdline));
kvm__arch_set_cmdline(real_cmdline, kvm->cfg.vnc || kvm->cfg.sdl || kvm->cfg.gtk);
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..43595b8 100644
--- a/util/threadpool.c
+++ b/util/threadpool.c
@@ -124,7 +124,7 @@ 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 = kvm->cfg.nrthreads;
running = true;
--
1.7.9.5
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