On 3/31/26 05:08, Collin Funk wrote:
I attached a v2 patch [...]
> Subject: [PATCH v2] cat: use splice if operating on non-files or if
> copy_file_range fails
>
> On a AMD Ryzen 7 3700X system:
>
> $ timeout 10 taskset 1 ./src/cat-prev /dev/zero \
> | taskset 2 pv -r > /dev/null
> [1.84GiB/s]
> $ timeout 10 taskset 1 ./src/cat /dev/zero \
> | taskset 2 pv -r > /dev/null
> [7.92GiB/s]
>
> On a Power10 system:
>
> $ taskset 1 ./src/yes | timeout 10 taskset 2 ./src/cat-prev \
> | taskset 3 pv -r > /dev/null
> [12.6GiB/s]
> $ taskset 1 ./src/yes | timeout 10 taskset 2 ./src/cat \
> | taskset 3 pv -r > /dev/null
> [61.3GiB/s]
The Power10 example references src/yes instead of src/cat.
> diff --git a/NEWS b/NEWS
> index 2fabd07b7..2411e64d2 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -39,6 +39,10 @@ GNU coreutils NEWS -*-
outline -*-
>
> ** Improvements
>
> + 'cat' now uses zero-copy I/O on Linux when the input or output are not
regular
> + files to significantly increase throughput.
> + E.g., throughput improved 5x from 12.6GiB/s to 61.3GiB/s on a Power10
system.
> +
"are not regular files" ... that sounds a bit vague.
AFAIU splice is used when at least one of either input or output is a pipe,
isn't it?
> diff --git a/src/cat.c b/src/cat.c
> index f9c92005c..11a2df450 100644
> --- a/src/cat.c
> +++ b/src/cat.c
[...]
> @@ -545,6 +548,109 @@ copy_cat (void)
> }
> }
>
> +/* Copy data from input to output using splice if possible.
> + Return 1 if successful, 0 if ordinary read+write should be tried,
> + -1 if a serious problem has been diagnosed. */
> +
> +static int
> +splice_cat (void)
> +{
> + bool some_copied = false;
[...]
> + return ok ? some_copied : -1;
> +}
This returns a bool as int.
I'd suggest sticking clearly to 'int' for clarity.
Have a nice day,
Berny
