Pettenò: Debunking x32 myths [LWN.net]

Pettenò: Debunking x32 myths

Posted Jun 26, 2012 10:11 UTC (Tue) by ebirdie (subscriber, #512)
In reply to: Pettenò: Debunking x32 myths by dlang
Parent article: Pettenò: Debunking x32 myths

Heh. Guite the opposite. On the laptop typing this text I managed to gain performance by changing to pure 32 bit system code with 64 bit kernel about a year ago. The laptop is equipped with 1G RAM. With pure 64 bit the system had frequent swap storms and hitting 1G RAM usage while keeping my basic set of programs open on Xfce desktop. With 32 bit system memory usage got under 512 meg. The change was made plain and simple: got tired to lock ups, managed to monitor, what was the cause while system was nearly or totally unresponsive (kswapd, RAM usage and usually occured when switching between applications), and finally system reinstall with 32 bit binaries. After reinstall RAM usage with normal apps loaded showed 470 megs and I've been happy user since although I have pure 64 bit systems, but their minimum RAM is 2 Gigs. .

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Pettenò: Debunking x32 myths

Posted Jun 26, 2012 11:21 UTC (Tue) by drag (subscriber, #31333) [Link]

Any performance gains I get by using x32 is going to be more then wiped out by any sort of time and effort it takes to deal with software incompatibilities caused by having a different ABI.

Pettenò: Debunking x32 myths

Posted Jun 26, 2012 19:20 UTC (Tue) by butlerm (subscriber, #13312) [Link]

Those applications would probably break a lot less if the decision was made to use L64P32 instead of ILP32. Is that too late to fix?

Pettenò: Debunking x32 myths

Posted Jun 26, 2012 21:00 UTC (Tue) by Flameeyes (subscriber, #51238) [Link]

It is. And it's one of my complaints, if you read the original article. They came up with this ABI too late in the game (most software has been soundly tested, or even entirely developed, on amd64), and with too little common points to either x86 or amd64 to make it easy to port.

So the (IMHO little) benefit on the data cache utilisation is made useless by the huge effort and compatibility issues brought in by having a full new ABI. Which is probably why the original presentation "sold" x32 as a closed-system ABI, not a generic one, like it seems people expect it to be right now.