[dm-devel] [PATCH] multipathd: "san_path_err" failure optimization

[Martin Wilck]

On Tue, 2019-08-27 at 12:28 +0000, Chongyun Wu wrote:
> Hi Martin and Ben,
> 
> Cloud you help to view below patch, thanks.
> 
> From a7126e33e7eff8a985600b41b1723ee66b183586 Mon Sep 17 00:00:00
> 2001
> From: Chongyun Wu <wu.chongyun at h3c.com>
> Date: Tue, 27 Aug 2019 10:23:50 +0800
> Subject: [PATCH] multipathd: "san_path_err" failure optimization
> 
> Let san_path_err_recovery_time path unstable can be
> detected and not reinstate it until this path keep up in
> san_path_err_recovery_time. It will fix heavy IO delay
> caused by parts of paths state shaky in multipath device.
> 
> Test and result:
> Run up eth1 30s and down eth1 30s with 100 loops script to
> make some paths shaky in each multipath devices.
> Using below multipath.conf configure in defaults section:
>     san_path_err_recovery_time 30
>     san_path_err_threshold 2
>     san_path_err_forget_rate 6
> After test, not found any IO delay logs except several logs in the
> very
> beginning which before san_path_err filter shaky path works .
> If without above config and this patch there will be lots of IO delay
> in syslog and some paths state change from up to down again and
> again.
> 
> Signed-off-by: Chongyun Wu <wu.chongyun at h3c.com>
> ---
>  multipathd/main.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 

Hello Chongyun,

Your patch makes sense to me. Ben has worked much more than myself on
marginal paths recently, so I'd want to see his opinion, too.

Regards,
Martin