What does sendfile_max_chunk do?

Igor Sysoev igor at sysoev.ru
Fri May 14 16:12:59 MSD 2010

On Fri, May 14, 2010 at 06:52:29AM -0400, Costello wrote:

> Hello,
> Once again I am in need of your help!
> I'm looking to document directives that are missing from the Wiki.
> I found loads in the source code, especially thanks to Manlio Perillo.
> I've stumbled upon "sendfile_max_chunk" declared in ngx_http_core_module.c.
> I investigated what this does, here is what I found:
> - it's a size value directive
> - it's set to 0 by default (presumably this means no maximum size)
> I'm not sure what it does. 
> It is probably somewhat connected to the use of sendfile, my understanding is as follows:
> "This directive defines the maximum size of chunks to be read from the storage system when using sendfile".
> Is this a correct and accurate definition? Could anyone provide more information?

On fast local connection sendfile() in Linux may send tens of megabytes
per one syscall blocking other connections. sendfile_max_chunk allows
to limit the maximum size per one sendfile() operation.

Igor Sysoev

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