On Wed, Dec 14, 2016 at 02:33:39PM +0000, zhangsha (A) wrote:
> Hi, all
>
> In my test scenario, I found that it takes too long time, 488s, to create 512
> bridges in ovs 2.5.0.
> After analyzing the code and some tests, I found that more than 70% of the
> time was consumed in the implementation of function xlate_txn_commit.
> Function type_run calls xlate_txn_start and xlate_txn_commit(calls
> ovsrcu_synchronize) to implement RCU locking in each cycle of the loop.
> Function ovsrcu_synchronize() was called too much times if there are certain
> number bridges, which means a lot of time waste.
>
> So, I was thinking if I can use ovsrcu_postpone replacing ovsrcu_synchronize
> to shorten the execution time of type_run when there are certain number
> bridges.
> I have tested this, and the result indicates that the time of creating 512
> bridges will be short down to 269s. Result and my patch is as follows:
>
>
> ovsrcu_postpone
>
> ovsrcu_synchronize
>
> ovs
>
> 269
>
> 488
>
>
>
> This is my patch:
> ofproto/ofproto-dpif-xlate.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
> index d5f18b6..59f4b5c 100644
> --- a/ofproto/ofproto-dpif-xlate.c
> +++ b/ofproto/ofproto-dpif-xlate.c
> @@ -865,8 +865,9 @@ xlate_txn_commit(void)
> struct xlate_cfg *xcfg = ovsrcu_get(struct xlate_cfg *, &xcfgp);
> ovsrcu_set(&xcfgp, new_xcfg);
> - ovsrcu_synchronize();
> - xlate_xcfg_free(xcfg);
> + ovsrcu_postpone(xlate_xcfg_free, xcfg);
> new_xcfg = NULL;
> }
>
> Whether this modification will introduce any problems?
Yes. See the following commit.
It sounds like you're creating each bridge in a separate database
transaction. If you create them in a single transaction, it will be
much faster.
--8<--------------------------cut here-------------------------->8--
>From 40a9c4c26be9b59c3494dd5900c21015ea7d27d4 Mon Sep 17 00:00:00 2001
From: Alex Wang <al...@nicira.com>
Date: Fri, 7 Nov 2014 13:02:05 -0800
Subject: [PATCH] ofproto-dpif-xlate: Allow direct destroy of previous config.
Before this commit, the ofproto-dpif-xlate module uses ovs-rcu to
postpone the destroy of previous configuration. However, the delayed
close of object like 'struct netdev' could cause failure in immediate
re-add or reconfigure of the same device.
To fix the above issue, this commit makes the ofproto-dpif-xlate
module call ovsrcu_synchronize(), which waits for all threads
to finish the use of reference to previous config. Then, the
module can just directly destroy the previous config.
Reported-by: Cian Ferriter <cian.ferri...@intel.com>
Signed-off-by: Alex Wang <al...@nicira.com>
Acked-by: Ben Pfaff <b...@nicira.com>
---
ofproto/ofproto-dpif-xlate.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index 6bf6d6d..f781bc5 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -672,8 +672,8 @@ xlate_txn_commit(void)
struct xlate_cfg *xcfg = ovsrcu_get(struct xlate_cfg *, &xcfgp);
ovsrcu_set(&xcfgp, new_xcfg);
- ovsrcu_postpone(xlate_xcfg_free, xcfg);
-
+ ovsrcu_synchronize();
+ xlate_xcfg_free(xcfg);
new_xcfg = NULL;
}
--
2.10.2
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