On 2016/4/26 15:45, Christian Borntraeger wrote:
On 04/26/2016 03:26 AM, Zhou Jie wrote:
net_init_tap has a huge stack usage of 8192 bytes approx.
Moving large arrays to heap to reduce stack usage.
I am wondering. Why is 8k a problem for a user space program?
For 64bit machine it will be 16k.
Please note that malloc/new like allocations are much more expensive
than stack allocation in terms of performance. This does not matter
here, but in your other patch that deals with the xmit function, I would
not be surprised if that actually harms performance.
OK. I will note it.
Sincerely,
Zhou Jie
Christian
Signed-off-by: Zhou Jie <zhoujie2...@cn.fujitsu.com>
---
net/tap.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/net/tap.c b/net/tap.c
index 740e8a2..49817c7 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -769,8 +769,8 @@ int net_init_tap(const NetClientOptions *opts, const char
*name,
return -1;
}
} else if (tap->has_fds) {
- char *fds[MAX_TAP_QUEUES];
- char *vhost_fds[MAX_TAP_QUEUES];
+ char **fds = g_new(char *, MAX_TAP_QUEUES);
+ char **vhost_fds = g_new(char *, MAX_TAP_QUEUES);
int nfds, nvhosts;
if (tap->has_ifname || tap->has_script || tap->has_downscript ||
@@ -818,6 +818,8 @@ int net_init_tap(const NetClientOptions *opts, const char
*name,
return -1;
}
}
+ g_free(fds);
+ g_free(vhost_fds);
} else if (tap->has_helper) {
if (tap->has_ifname || tap->has_script || tap->has_downscript ||
tap->has_vnet_hdr || tap->has_queues || tap->has_vhostfds) {
--
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