linux-kernel - Re: [PATCH v5 0/6] fs/dcache: Track & limit # of negative dentries

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Message-ID: <8e40fee3-4a6a-244d-aa9b-97123b56e6fb@redhat.com>
Date:   Tue, 3 Jul 2018 08:46:07 +0800
From:   Waiman Long <longman@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Jan Kara <jack@...e.cz>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Larry Woodman <lwoodman@...hat.com>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        "Wangkai (Kevin,C)" <wangkai86@...wei.com>
Subject: Re: [PATCH v5 0/6] fs/dcache: Track & limit # of negative dentries

On 07/03/2018 03:34 AM, Linus Torvalds wrote:
> On Sun, Jul 1, 2018 at 10:52 PM Waiman Long <longman@...hat.com> wrote:
>> A rogue application can potentially create a large number of negative
>> dentries in the system consuming most of the memory available if it
>> is not under the direct control of a memory controller that enforce
>> kernel memory limit.
> I certainly don't mind the patch series, but I would like it to be
> accompanied with some actual example numbers, just to make it all a
> bit more concrete.
>
> Maybe even performance numbers showing "look, I've filled the dentry
> lists with nasty negative dentries, now it's all slower because we
> walk those less interesting entries".
>
>               Linus

I did have performance numbers in the previous version of the patchset.
I will rerun the performance test and post the numbers later on.

Cheers,
Longman