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From:   Shakeel Butt <shakeelb@google.com>
Date:   Wed, 21 Aug 2019 17:17:14 -0700
Message-ID: <CALvZod44CHWEUxa4Mi7nRLfgyCnGgNAxso8SLA5xVoR=DdQiWw@mail.gmail.com>
Subject: Re: [PATCH 1/3] fuse: on 64-bit store time in d_fsdata directly
To:     Khazhismel Kumykov <khazhy@google.com>
Cc:     miklos@szeredi.hu, linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Aug 21, 2019 at 5:09 PM Khazhismel Kumykov <khazhy@google.com> wrote:
>
> Implements the optimization noted in f75fdf22b0a8 ("fuse: don't use
> ->d_time"), as the additional memory can be significant. (In particular,
> on SLAB configurations this 8-byte alloc becomes 32 bytes). Per-dentry,
> this can consume significant memory.
>
> Signed-off-by: Khazhismel Kumykov <khazhy@google.com>

Actually we are seeing this in production where a job creating a lot
of fuse files cause a lot of extra system level overhead.

Reviewed-by: Shakeel Butt <shakeelb@google.com>

> ---
>  fs/fuse/dir.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> index dd0f64f7bc06..f9c59a296568 100644
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@ -24,6 +24,18 @@ static void fuse_advise_use_readdirplus(struct inode *dir)
>         set_bit(FUSE_I_ADVISE_RDPLUS, &fi->state);
>  }
>
> +#if BITS_PER_LONG >= 64
> +static inline void fuse_dentry_settime(struct dentry *entry, u64 time)
> +{
> +       entry->d_fsdata = (void *) time;
> +}
> +
> +static inline u64 fuse_dentry_time(struct dentry *entry)
> +{
> +       return (u64)entry->d_fsdata;
> +}
> +
> +#else
>  union fuse_dentry {
>         u64 time;
>         struct rcu_head rcu;
> @@ -38,6 +50,7 @@ static inline u64 fuse_dentry_time(struct dentry *entry)
>  {
>         return ((union fuse_dentry *) entry->d_fsdata)->time;
>  }
> +#endif
>
>  /*
>   * FUSE caches dentries and attributes with separate timeout.  The
> @@ -242,6 +255,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
>         goto out;
>  }
>
> +#if BITS_PER_LONG < 64
>  static int fuse_dentry_init(struct dentry *dentry)
>  {
>         dentry->d_fsdata = kzalloc(sizeof(union fuse_dentry), GFP_KERNEL);
> @@ -254,16 +268,21 @@ static void fuse_dentry_release(struct dentry *dentry)
>
>         kfree_rcu(fd, rcu);
>  }
> +#endif
>
>  const struct dentry_operations fuse_dentry_operations = {
>         .d_revalidate   = fuse_dentry_revalidate,
> +#if BITS_PER_LONG < 64
>         .d_init         = fuse_dentry_init,
>         .d_release      = fuse_dentry_release,
> +#endif
>  };
>
>  const struct dentry_operations fuse_root_dentry_operations = {
> +#if BITS_PER_LONG < 64
>         .d_init         = fuse_dentry_init,
>         .d_release      = fuse_dentry_release,
> +#endif
>  };
>
>  int fuse_valid_type(int m)
> --
> 2.23.0.187.g17f5b7556c-goog
>