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
>From 63b276ed881c1e2a89b7ea35b6f328f70ddd6185 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..397d86a 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)
--
1.8.3.1
