linux-kernel - Re: [PATCH 06/13] blkcg: add generic throttling mechanism

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 5 Jun 2018 13:45:56 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Josef Bacik <josef@...icpanda.com>
Cc:     axboe@...nel.dk, kernel-team@...com, linux-block@...r.kernel.org,
        akpm@...ux-foundation.org, hannes@...xchg.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Josef Bacik <jbacik@...com>
Subject: Re: [PATCH 06/13] blkcg: add generic throttling mechanism

On Tue, Jun 05, 2018 at 09:29:41AM -0400, Josef Bacik wrote:
> From: Josef Bacik <jbacik@...com>
> 
> Since IO can be issued from literally anywhere it's almost impossible to
> do throttling without having some sort of adverse effect somewhere else
> in the system because of locking or other dependencies.  The best way to
> solve this is to do the throttling when we know we aren't holding any
> other kernel resources.  Do this by tracking throttling in a per-blkg
> basis, and if we require throttling flag the task that it needs to check
> before it returns to user space and possibly sleep there.
> 
> This is to address the case where a process is doing work that is
> generating IO that can't be throttled, whether that is directly with a
> lot of REQ_META IO, or indirectly by allocating so much memory that it
> is swamping the disk with REQ_SWAP.  We can't use task_add_work as we
> don't want to induce a memory allocation in the IO path, so simply
> saving the request queue in the task and flagging it to do the
> notify_resume thing achieves the same result without the overhead of a
> memory allocation.
> 
> Signed-off-by: Josef Bacik <jbacik@...com>

Acked-by: Tejun Heo <tj@...nel.org>

-- 
tejun