Ted Ts'o wrote:
> Thanks for the commit. Since we don't have support for fs block size
>> page size (and having done a private investigation about what would
> be required, I'm not sure it's going to happen any time soon --- and
> if it does, yanking the #if statements is going to be a tiny part of
> the patch :-).
>
> So I slightly modified your patch to only do the extra complexity if
> the page size is >= 65536.
I had resisted doing that because at least the original rationale in
the patch was for when the VM allows block size > page size ...
Side note, if you do this is PAGE_SIZE or PAGE_CACHE_SIZE the right macro?
-Eric
> - Ted
>
> commit 097639d271f40376f3b3a94c7ab242c22ddc8bc1
> Author: Eric Sandeen <sandeen@xxxxxxxxxx>
> Date: Wed Aug 4 20:09:07 2010 -0400
>
> ext4: re-inline ext4_rec_len_(to|from)_disk functions
>
> commit 3d0518f4, "ext4: New rec_len encoding for very
> large blocksizes" made several changes to this path, but from
> a perf perspective, un-inlining ext4_rec_len_from_disk() seems
> most significant. This function is called from ext4_check_dir_entry(),
> which on a file-creation workload is called extremely often.
>
> I tested this with bonnie:
>
> # bonnie++ -u root -s 0 -f -x 200 -d /mnt/test -n 32
>
> (this does 200 iterations) and got this for the file creations:
>
> ext4 stock: Average = 21206.8 files/s
> ext4 inlined: Average = 22346.7 files/s (+5%)
>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index ed14e1d..0f340bf 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1412,6 +1412,43 @@ struct ext4_dir_entry_2 {
> #define EXT4_MAX_REC_LEN ((1<<16)-1)
>
> /*
> + * If we ever get support for fs block sizes > page_size, we'll need
> + * to remove the #if statements in the next two functions...
> + */
> +static inline unsigned int
> +ext4_rec_len_from_disk(__le16 dlen, unsigned blocksize)
> +{
> + unsigned len = le16_to_cpu(dlen);
> +
> +#if (PAGE_SIZE >= 65536)
> + if (len == EXT4_MAX_REC_LEN || len == 0)
> + return blocksize;
> + return (len & 65532) | ((len & 3) << 16);
> +#else
> + return len;
> +#endif
> +}
> +
> +static inline __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
> +{
> + if ((len > blocksize) || (blocksize > (1 << 18)) || (len & 3))
> + BUG();
> +#if (PAGE_SIZE >= 65536)
> + if (len < 65536)
> + return cpu_to_le16(len);
> + if (len == blocksize) {
> + if (blocksize == 65536)
> + return cpu_to_le16(EXT4_MAX_REC_LEN);
> + else
> + return cpu_to_le16(0);
> + }
> + return cpu_to_le16((len & 65532) | ((len >> 16) & 3));
> +#else
> + return cpu_to_le16(len);
> +#endif
> +}
> +
> +/*
> * Hash Tree Directory indexing
> * (c) Daniel Phillips, 2001
> */
> @@ -1636,8 +1673,6 @@ extern long ext4_compat_ioctl(struct file *, unsigned int, unsigned long);
> extern int ext4_ext_migrate(struct inode *);
>
> /* namei.c */
> -extern unsigned int ext4_rec_len_from_disk(__le16 dlen, unsigned blocksize);
> -extern __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize);
> extern int ext4_orphan_add(handle_t *, struct inode *);
> extern int ext4_orphan_del(handle_t *, struct inode *);
> extern int ext4_htree_fill_tree(struct file *dir_file, __u32 start_hash,
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index ea8b59d..314c0d3 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -179,30 +179,6 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
> static int ext4_dx_add_entry(handle_t *handle, struct dentry *dentry,
> struct inode *inode);
>
> -unsigned int ext4_rec_len_from_disk(__le16 dlen, unsigned blocksize)
> -{
> - unsigned len = le16_to_cpu(dlen);
> -
> - if (len == EXT4_MAX_REC_LEN || len == 0)
> - return blocksize;
> - return (len & 65532) | ((len & 3) << 16);
> -}
> -
> -__le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
> -{
> - if ((len > blocksize) || (blocksize > (1 << 18)) || (len & 3))
> - BUG();
> - if (len < 65536)
> - return cpu_to_le16(len);
> - if (len == blocksize) {
> - if (blocksize == 65536)
> - return cpu_to_le16(EXT4_MAX_REC_LEN);
> - else
> - return cpu_to_le16(0);
> - }
> - return cpu_to_le16((len & 65532) | ((len >> 16) & 3));
> -}
> -
> /*
> * p is at least 6 bytes before the end of page
> */
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