On 11 December 2012 12:36, Frank Steinmetzger <[email protected]> wrote: > Hello list . . . > So I’m interested in you opinion and own experience about the following > arising questions: > > * From my observations, the benefit of 64 bit over 32 is much smaller for an > Atom than it is for my Core2. Am I right to assume thus that the Atom > architecture doesn’t have much to offer to 64 bit (such as extra registers)? > I’m not talking about memory here, since it’s limited to 2 GB in any case. > > * The problem of distcc between different architectures: > The netbook already had an older 32 bit Gentoo installed. And since I have > a multilib host (march=core2), I though I could upgrade with distcc (using > march=atom on the netbook). But at some point more and more stuff stopped > working, eventually I got “invalid instruction” errors during emerge, hence > I figured that was a dead end. > > So is it possible to mix architectures in this way at all with distcc? > I also have crossdev for i686 installed, which even shares files with the > system’s normal multilib gcc. I find that odd. > I sped up the installation process for 32 bit by using a chroot on the big > machine, which worked nicely. But it’s not a long-term solution, b/c it > uses up too much disk space on the host. > > * I’m interested in the question of -O2 vs. -Os. > Some sources say -Os is bad, b/c it breaks debugging and is mainly untested. > I won’t do heavy developing on it anyway, and Atoms do have a puny cache. > So I wonder whether -Os would improve execution time and RAM usage > noticably. Diskspace itself is not an issue. > > * I’m also interested in comparing bin packages over self-compiled ones. > E.g. I did compile icedtea, even if it’s just for TV browser. :) > Can you name a Java benchmark to measure CPU performance? > > * The last thing I’m going to set up is filesystem encryption, at least for ~. > I already know/think that AES would be the best choice due to limited CPU > power, but what else is there to heed besides key size? > > * What other small benchmarks for CPU and memory can you recommend? So far I > tested with nbench and sysbench. The results are so-and-so. Some computation > stuff is much slower on 64 bit, some a bit faster. The applicability to > every-day use is of course a wibbly-wobbly argument. > I also tested the runtime of some application (packing and unpacking of > archives, throughput with dd, mencoder). If there is interest, I can post > the result of 21 runs on each platform, measured with GNU time. > > ----------[ Questions end ]-------------------------------------------------- > > > PS.: I’m aware that benchmarks are always a bit subjective and none is > perfect. I also realise that most of the questions quite belong into the > ricer corner. But Netbooks are ricer devices, b/c they need to perform at > their limits all the time. :-D >
I have an old N280 atom netbook, so the 64v32 is moot for me, but with a hardware limit of 2G, I'd probably run 32-bit. I don't use distcc, either, since I'd rather not saturate my (802.11g) wireless network. -Os, in my experience, makes very little difference on amd64/x86_64/whate'er (FreeBSD 9.x amd64 clang the final sizes of the binaries between -Os & -O3 have very little bearing on expectations), however the atom seems to benefit quite a lot more from the smaller binaries, which on 32-bit (again in my experience with gentoo gcc46 i686) are significantly smaller than -O2 & -O3 binaries. I would assume this has to do with cache fit. Some suggest using -mfpmath=sse, which I've not studied in depth. But if the x87 bits are particularly slow on the atom (mind you, I have no idea), & you're not running stuff that makes heavy use of your sse registers I don't see a downside. 64-bit probably won't help much at all, unless you're running really numbery stuff. I suggest unless you're doing video editing or scientific number crunching (on your atom netbook) 32 will be fine.
