[PATCH] [DISCUSS] Optimizing linux applications with the help of the kernel.

[PATCH] [DISCUSS] Optimizing linux applications with the help of the kernel.

[Amit Choudhary]

Hi All,

I just had an idea for improving the performance of linux applications with some help from the
kernel. Let's say that I have to make a copy of a file. So, I read the input file into a buffer
and then write the buffer to the output file.

In both these cases the same data is coming from kernel_to_user and then from user_to_kernel. If
this can be short-circuited, that is, from kernel_to_kernel then the performance can be increased
a lot.

The psuedocode would be:

fd_inp = open _output_file
fd_out = open _input_file
instruct_kernel to write next data read from fd_inp to fd_out
read fd_out

The same mechanism can be applied to many other scenarios.
May be whatever I am thinking is wrong or involves lot of complexities but this is just a thought.

Regards,
Amit



 
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Re: [PATCH] [DISCUSS] Optimizing linux applications with the help of the kernel.

[bert hubert]

On Sun, Dec 10, 2006 at 02:06:49AM -0800, Amit Choudhary wrote:
> In both these cases the same data is coming from kernel_to_user and then from user_to_kernel. If
> this can be short-circuited, that is, from kernel_to_kernel then the performance can be increased
> a lot.

Google on 'splice linux'. It can't do what you want right now exactly, but
it might.

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Re: [PATCH] [DISCUSS] Optimizing linux applications with the help of the kernel.

[Benoit Boissinot]

On 12/10/06, Amit Choudhary <amit2030@yahoo.com> wrote:
> Hi All,
>
> I just had an idea for improving the performance of linux applications with some help from the
> kernel. Let's say that I have to make a copy of a file. So, I read the input file into a buffer
> and then write the buffer to the output file.
>
> In both these cases the same data is coming from kernel_to_user and then from user_to_kernel. If
> this can be short-circuited, that is, from kernel_to_kernel then the performance can be increased
> a lot.
>
> The psuedocode would be:
>
> fd_inp = open _output_file
> fd_out = open _input_file
> instruct_kernel to write next data read from fd_inp to fd_out
> read fd_out
>
>
I think you are describing the splice syscall:

see http://lwn.net/Articles/178199/

regards,

Benoit

Re: [PATCH] [DISCUSS] Optimizing linux applications with the help of the kernel.

[Jesper Juhl]

On 10/12/06, Amit Choudhary <amit2030@yahoo.com> wrote:
> Hi All,
>
> I just had an idea for improving the performance of linux applications with some help from the
> kernel. Let's say that I have to make a copy of a file. So, I read the input file into a buffer
> and then write the buffer to the output file.
>
> In both these cases the same data is coming from kernel_to_user and then from user_to_kernel. If
> this can be short-circuited, that is, from kernel_to_kernel then the performance can be increased
> a lot.
>

See the linux specific splice() syscall - "man 2 splice".

-- 
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