netdev - Re: [PATCH net] cgroup, netclassid: periodically release file

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Date:   Mon, 09 Mar 2020 18:14:20 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     zeil@...dex-team.ru
Cc:     netdev@...r.kernel.org, khlebnikov@...dex-team.ru
Subject: Re: [PATCH net] cgroup, netclassid: periodically release file_lock
 on classid updating

From: Dmitry Yakunin <zeil@...dex-team.ru>
Date: Thu, 5 Mar 2020 17:45:57 +0300

> In our production environment we have faced with problem that updating
> classid in cgroup with heavy tasks cause long freeze of the file tables
> in this tasks. By heavy tasks we understand tasks with many threads and
> opened sockets (e.g. balancers). This freeze leads to an increase number
> of client timeouts.
> 
> This patch implements following logic to fix this issue:
> аfter iterating 1000 file descriptors file table lock will be released
> thus providing a time gap for socket creation/deletion.
> 
> Now update is non atomic and socket may be skipped using calls:
> 
> dup2(oldfd, newfd);
> close(oldfd);
> 
> But this case is not typical. Moreover before this patch skip is possible
> too by hiding socket fd in unix socket buffer.
> 
> New sockets will be allocated with updated classid because cgroup state
> is updated before start of the file descriptors iteration.
> 
> So in common cases this patch has no side effects.
> 
> Signed-off-by: Dmitry Yakunin <zeil@...dex-team.ru>
> Reviewed-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>

Applied and queued up for -stable, thank you.