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From Zhe Zhang <zhezh...@us.ibm.com>
Subject Re: Question about httpd memory buffer alignment
Date Fri, 11 Jan 2013 18:54:24 GMT

Ben Reser <ben@reser.org> wrote on 01/11/2013 01:45:43 PM:

> From: Ben Reser <ben@reser.org>
> To: Zhe Zhang/Watson/IBM@IBMUS,
> Cc: dev@apr.apache.org
> Date: 01/11/2013 01:46 PM
> Subject: Re: Question about httpd memory buffer alignment
>
> On Fri, Jan 11, 2013 at 7:28 AM, Zhe Zhang <zhezhang@us.ibm.com> wrote:
> > I would like httpd to use 4K-aligned buffers so that I can do direct
I/O on
> > the html files being served. Could anyone tell me which file I need to
> > modify? I've already changed APR_BUCKET_BUFF_SIZE to 8192 so at least
the
> > buffer size is multiple of 4K.
>
> If that isn't doing what you want then there are two possible places
> that the read is happening.

Hi Ben, thank you for the reply. I have disabled mmap and sendfile options.
I'm getting 8192 bytes buffers; so the size is fine, but I want the
starting address of the buffer to be 4K-aligned too. Now it seems aligned
at 8 bytes boundary (xxxxx8 instead of xxxx000).

>
> 1) Memory mapping is enabled and then the file is read by the kernel
> via the mmap system call.  See file_make_mmap() in APR's
> buckets/apr_buckets_file.c.
>
> You can disable this with EnableMMAP off configuration directive to
httpd.
>
> 2) Sendfile support is enabled and then the file is read by the kernel
> via the sendfile system call.  See send_brigade_nonblocking() in
> httpd's server/core_filters.c.
>
> You can disable this with EnableSendfile off configuration directiveto
httpd.
>
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