Re: [PATCH 08/12] libmultipath: wait one seconds for more uevents in uevent_listen() in uevents burst situations

[Martin Wilck <mwilck@suse.com>]

On Tue, 2016-12-27 at 16:03 +0800, tang.junhui@zte.com.cn wrote:
> From: tang.junhui <tang.junhui@zte.com.cn>
> 
> The more uevents are merged, the higher efficiency program will
> performs.
> So, do not process uevents after receiving immediately in uevents
> burst
> situations, but continue wait 1 seconds for more uevents except that
> too
> much uevents (2048) have already been received or too much time
> eclipse
> (60 seconds).

Hi Tang,

thanks for this impressive patch set. While I haven't had time to read
through the more complex parts yet, one small nitpick on this patch:
please use named constants rather than explicit numbers in the code.

Regards,
Martin


> 
> Change-Id: I763d491540e8114a81d12d603281540a81502742
> Signed-off-by: tang.junhui <tang.junhui@zte.com.cn>
> ---
>  libmultipath/uevent.c | 35 +++++++++++++++++++++++++++++++++--
>  1 file changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
> index cc10d65..b0b05e9 100644
> --- a/libmultipath/uevent.c
> +++ b/libmultipath/uevent.c
> @@ -39,6 +39,7 @@
>  #include <linux/netlink.h>
>  #include <pthread.h>
>  #include <sys/mman.h>
> +#include <sys/time.h>
>  #include <libudev.h>
>  #include <errno.h>
>  
> @@ -490,11 +491,37 @@ struct uevent *uevent_from_udev_device(struct
> udev_device *dev)
>  	return uev;
>  }
>  
> +bool uevent_burst(struct timeval *start_time, int events)
> +{
> +	struct timeval diff_time, end_time;
> +	unsigned long speed;
> +	unsigned long eclipse_ms;
> +
> +	gettimeofday(&end_time, NULL);
> +	timersub(&end_time, start_time, &diff_time);
> +
> +	eclipse_ms = diff_time.tv_sec * 1000 + diff_time.tv_usec /
> 1000;
> +	if (eclipse_ms == 0)
> +		return true;
> +	/* max wait 60s */
> +	if (eclipse_ms > 60*1000) {
> +		condlog(1, "burst continued =%lu ms, stoped",
> eclipse_ms);
> +		return false;
> +	}
> +
> +	speed = (events * 1000) / eclipse_ms;
> +	if (speed > 10)
> +		return true;
> +
> +	return false;
> +}
> +
>  int uevent_listen(struct udev *udev)
>  {
>  	int err = 2;
>  	struct udev_monitor *monitor = NULL;
>  	int fd, socket_flags, events;
> +	struct timeval start_time;
>  	int need_failback = 1;
>  	int timeout = 30;
>  	LIST_HEAD(uevlisten_tmp);
> @@ -548,6 +575,7 @@ int uevent_listen(struct udev *udev)
>  	}
>  
>  	events = 0;
> +	gettimeofday(&start_time, NULL);
>  	while (1) {
>  		struct uevent *uev;
>  		struct udev_device *dev;
> @@ -562,7 +590,8 @@ int uevent_listen(struct udev *udev)
>  		errno = 0;
>  		fdcount = poll(&ev_poll, 1, poll_timeout);
>  		if (fdcount && ev_poll.revents & POLLIN) {
> -			timeout = 0;
> +			timeout = uevent_burst(&start_time, events +
> 1) ? 1:0;
> +
>  			dev = udev_monitor_receive_device(monitor);
>  			if (!dev) {
>  				condlog(0, "failed getting udev
> device");
> @@ -578,7 +607,8 @@ int uevent_listen(struct udev *udev)
>  			}
>  			list_add_tail(&uev->node, &uevlisten_tmp);
>  			events++;
> -			continue;
> +			if(events < 2048)
> +				continue;
>  		}
>  		if (fdcount < 0) {
>  			if (errno == EINTR)
> @@ -600,6 +630,7 @@ int uevent_listen(struct udev *udev)
>  			pthread_mutex_unlock(uevq_lockp);
>  			events = 0;
>  		}
> +		gettimeofday(&start_time, NULL);
>  		timeout = 30;
>  	}
>  	need_failback = 0;

-- 
Dr. Martin Wilck <mwilck@suse.com>, Tel. +49 (0)911 74053 2107
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton
HRB 21284 (AG Nürnberg)

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