[OpenWrt-Devel] Toolchain issue: Significant decrease in performance of binaries produced by Barrier Breaker relative to Attitude Adjustment

[Hannu Nyman]

 > This could be a problem caused by mips16. We use that in BB to create
smaller binaries. but Jonas saw a performance problem in some
applications, mostly stuff doing crypto (big integer calculations).

Have developers evaluated the pros and cons of using mips16 as the default?

It was made the default along the switch to gcc4.8, but I do not remember 
seeing any extensive discussion about that change. Yes, it produces smaller 
binaries, but apparently with a visible performance hit.

The performance problems can materialize in strange ways, e.g. ssh login time 
to dropbear doubled (increased by several seconds), 
https://dev.openwrt.org/ticket/15209 . So, it is not just about gradual 
performance hit, but it can apparently cause visible annoyances.

Now that the performance issues have been noticed, is there any plan for 
developers to systematically go through the core apps to check the impact and 
turn mips16 off for problematic apps? I guess that based by evedence so far, 
it might be turned off for all math-intensive apps like crypto libraries, but 
there may be also others (maybe voice & image encoding/decoding?)

To have small binaries is nice, but I guess that a growing amount of Openwrt 
users are power users with modern routers with more flash space and having 
interest for VPNs etc. And for them mips16 may have brought more trouble than 
benefits.
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