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From Yann Ylavic <ylavic....@gmail.com>
Subject Re: httpd 2.4.25, mpm_event, ssl: segfaults
Date Wed, 15 Feb 2017 23:31:57 GMT
On Thu, Feb 16, 2017 at 12:06 AM, Jacob Champion <champion.p@gmail.com> wrote:
> On 02/15/2017 02:03 PM, Yann Ylavic wrote:
>
>> Assuming so :) there is also the fact that mod_ssl will encrypt/pass
>> 8K buckets at a time, while the core output filter tries to send the
>> whole mmap()ed file, keeping what remains after EAGAIN for the next
>> call (if any).
>
> Oh, right... we split on APR_MMAP_LIMIT in the mmap() case. Which is a nice
> big 4MiB instead of 8KiB. Could it really be as easy as tuning the default
> file bucket size up?

Actually this is 16K (the maximum size of a TLS record), so 16K
buckets are passed to the core output filter (which itself bufferizes
buckets lower than THRESHOLD_MIN_WRITE=4K, up to
THRESHOLD_MAX_BUFFER=64K before sending.

Without SSL, sending is done up to the size of the mmapp()ed file
still, which may make a difference.

Maybe you could try to play with
THRESHOLD_MIN_WRITE/THRESHOLD_MAX_BUFFER in server/core_filters.c for
the SSL case (e.g. MIN=4M and MAX=16M), but that'd still cost some
transient to heap buckets (copies) which don't happen in the non-SSL
case...
>
> --Jacob

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