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From Jacob Champion <champio...@gmail.com>
Subject Re: httpd 2.4.25, mpm_event, ssl: segfaults
Date Wed, 15 Feb 2017 23:06:41 GMT
On 02/15/2017 02:03 PM, Yann Ylavic wrote:
> On Wed, Feb 15, 2017 at 9:50 PM, Jacob Champion <champion.p@gmail.com> wrote:
>>
>> For the next step, I want to find out why TLS connections see such a big
>> performance hit when I switch off mmap(), but unencrypted connections
>> don't... it's such a huge difference that I feel like I must be missing
>> something obvious.
>
> First, you did "EnableSendfile off", right?

Yep :) But thanks for the reminder anyway; I would have kicked myself...

Also, I have to retract an earlier claim I made: I am now seeing a 
difference between the performance of mmap'd and non-mmap'd responses 
for regular HTTP connections. I don't know if I actually changed 
something, or if the original lack of difference was tester error on my 
part.

> 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?

--Jacob

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