On Tue, Jan 09, 2018 at 08:13:39AM +0100, Thomas Trepl wrote:
> Interesting that Intel (https://newsroom.intel.de/news-releases/industr
> y-testing-shows-recently-released-security-updates-not-impacting-
> performance-real-world-deployments/) thinks that there is no
> performance issue.
>
> Meassuring LFS builds looks a bit different to me (column 2+3 are build
> times in seconds and may not be 100% accurate but the trend is clear):
>
A few questions:
1. Is this building the same versions, but just using a different
kernel ? Actually, I thought PTI was _perhaps_ available on
4.14.10.
In general, single builds are anecdotal - I often find that - even
without obvious background activity (e.g. cron jobs, browser
activity) a build can vary by a few seconds.
The ideal would be to repeat the build a few time for both PTI and
nopti - I don't have time to do that, so I'm not proposing that
anyone else should, just mentioning that a single time is not
definitive.
2. Do you have newer firmware (to mitigate Spectre) ? That is the
thing which intel kernel developers think will slow things down.
3. For Meltdown (PTI) the main impacted use cases appear to be web
servers (with lots of network connections), databases, general
networking throughput on a currently-adequate system.
For the moment, I'll only comment on one of these -
> 300-linux-kernel 4079 4654 1,14
That is the sort of thing to make kernel developers go 'ouch!'.
On my own tests (haswell -j8, SandyBridge -j4) there was very little
difference with and without PTI.
ĸen
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