netdev - Re: [External] Re: [PATCH] files: Use rcu lock to get the file structures for better performance

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Message-ID: <CAMZfGtVxPevhTy8LMpKUtkk1jX86doiPD0nOTRuKg25+8Vz=ag@mail.gmail.com>
Date:   Fri, 22 May 2020 00:06:46 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     adobriyan@...il.com, ast@...nel.org, daniel@...earbox.net,
        kafai@...com, songliubraving@...com, yhs@...com, andriin@...com,
        john.fastabend@...il.com, kpsingh@...omium.org,
        ebiederm@...ssion.com, bernd.edlinger@...mail.de,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [External] Re: [PATCH] files: Use rcu lock to get the file
 structures for better performance

On Thu, May 21, 2020 at 11:21 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Thu, May 21, 2020 at 08:38:35PM +0800, Muchun Song wrote:
> > There is another safe way to get the file structure without
> > holding the files->file_lock. That is rcu lock, and this way
> > has better performance. So use the rcu lock instead of the
> > files->file_lock.
>
> What makes you think this is safe?  Are you actually seeing contention
> on this spinlock?
>

I have read the doc which is in the Documentation/filesystems/files.txt.
If my understanding is correct, I think it is safe to use rcu lock.

Thanks.

-- 
Yours,
Muchun