On 2017年09月18日 11:13, Jason Wang wrote:
On 2017年09月16日 03:19, Matthew Rosato wrote:
It looks like vhost is slowed down for some reason which leads to more
idle time on 4.13+VHOST_RX_BATCH=1. Appreciated if you can collect the
perf.diff on host, one for rx and one for tx.
perf data below for the associated vhost threads, baseline=4.12,
delta1=4.13, delta2=4.13+VHOST_RX_BATCH=1
Client vhost:
60.12% -11.11% -12.34% [kernel.vmlinux] [k] raw_copy_from_user
13.76% -1.28% -0.74% [kernel.vmlinux] [k] get_page_from_freelist
2.00% +3.69% +3.54% [kernel.vmlinux] [k] __wake_up_sync_key
1.19% +0.60% +0.66% [kernel.vmlinux] [k] __alloc_pages_nodemask
1.12% +0.76% +0.86% [kernel.vmlinux] [k] copy_page_from_iter
1.09% +0.28% +0.35% [vhost] [k] vhost_get_vq_desc
1.07% +0.31% +0.26% [kernel.vmlinux] [k] alloc_skb_with_frags
0.94% +0.42% +0.65% [kernel.vmlinux] [k] alloc_pages_current
0.91% -0.19% -0.18% [kernel.vmlinux] [k] memcpy
0.88% +0.26% +0.30% [kernel.vmlinux] [k] __next_zones_zonelist
0.85% +0.05% +0.12% [kernel.vmlinux] [k] iov_iter_advance
0.79% +0.09% +0.19% [vhost] [k] __vhost_add_used_n
0.74% [kernel.vmlinux] [k] get_task_policy.part.7
0.74% -0.01% -0.05% [kernel.vmlinux] [k] tun_net_xmit
0.60% +0.17% +0.33% [kernel.vmlinux] [k] policy_nodemask
0.58% -0.15% -0.12% [ebtables] [k] ebt_do_table
0.52% -0.25% -0.22% [kernel.vmlinux] [k] __alloc_skb
...
0.42% +0.58% +0.59% [kernel.vmlinux] [k] eventfd_signal
...
0.32% +0.96% +0.93% [kernel.vmlinux] [k] finish_task_switch
...
+1.50% +1.16% [kernel.vmlinux] [k] get_task_policy.part.9
+0.40% +0.42% [kernel.vmlinux] [k] __skb_get_hash_symmetr
+0.39% +0.40% [kernel.vmlinux] [k] _copy_from_iter_full
+0.24% +0.23% [vhost_net] [k] vhost_net_buf_peek
Server vhost:
61.93% -10.72% -10.91% [kernel.vmlinux] [k] raw_copy_to_user
9.25% +0.47% +0.86% [kernel.vmlinux] [k] free_hot_cold_page
5.16% +1.41% +1.57% [vhost] [k] vhost_get_vq_desc
5.12% -3.81% -3.78% [kernel.vmlinux] [k] skb_release_data
3.30% +0.42% +0.55% [kernel.vmlinux] [k] raw_copy_from_user
1.29% +2.20% +2.28% [kernel.vmlinux] [k] copy_page_to_iter
1.24% +1.65% +0.45% [vhost_net] [k] handle_rx
1.08% +3.03% +2.85% [kernel.vmlinux] [k] __wake_up_sync_key
0.96% +0.70% +1.10% [vhost] [k] translate_desc
0.69% -0.20% -0.22% [kernel.vmlinux] [k] tun_do_read.part.10
0.69% [kernel.vmlinux] [k] tun_peek_len
0.67% +0.75% +0.78% [kernel.vmlinux] [k] eventfd_signal
0.52% +0.96% +0.98% [kernel.vmlinux] [k] finish_task_switch
0.50% +0.05% +0.09% [vhost] [k] vhost_add_used_n
...
+0.63% +0.58% [vhost_net] [k] vhost_net_buf_peek
+0.32% +0.32% [kernel.vmlinux] [k] _copy_to_iter
+0.19% +0.19% [kernel.vmlinux] [k] __skb_get_hash_symmetr
+0.11% +0.21% [vhost] [k] vhost_umem_interval_tr
Looks like for some unknown reason which leads more wakeups.
Could you please try to attached patch to see if it solves or mitigate
the issue?
Thanks
My bad, please try this.
Thanks
>From 8be3edfcd415ba6157ab34d250127c6f2b21ff5d Mon Sep 17 00:00:00 2001
From: Jason Wang <jasow...@redhat.com>
Date: Mon, 18 Sep 2017 10:56:30 +0800
Subject: [PATCH] vhost_net: conditionally enable tx polling
Signed-off-by: Jason Wang <jasow...@redhat.com>
---
drivers/vhost/net.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 58585ec..2b308e0 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -471,6 +471,7 @@ static void handle_tx(struct vhost_net *net)
goto out;
vhost_disable_notify(&net->dev, vq);
+ vhost_net_disable_vq(net, vq);
hdr_size = nvq->vhost_hlen;
zcopy = nvq->ubufs;
@@ -562,6 +563,8 @@ static void handle_tx(struct vhost_net *net)
% UIO_MAXIOV;
}
vhost_discard_vq_desc(vq, 1);
+ if (err == -EAGAIN)
+ vhost_net_enable_vq(net, vq);
break;
}
if (err != len)
--
2.7.4
