Re: Unaligned access trade-offs for SFrame FRE layout

Jan Beulich <[email protected]> Sun, 14 Sep 2025 16:14:33 +0200
Newsgroups org.kernel.vger.linux-toolchains
Message-ID <[email protected]>
On 12.09.2025 19:34, Indu Bhagat via Binutils wrote:
> TL;DR: Thinking and experimenting a bit on the possible approaches for 
> avoiding unaligned accesses in the SFrame FRE layout (in SFrame V3), I 
> am not convinced that avoiding unaligned accesses for performance is 
> worth it.  IMO, forsaking compactness for avoiding unaligned accesses is 
> not a good trade off for SFrame.
> 
> Problem Statement
> On architectures such as x86_64, AArch64, and s390x, unaligned memory 
> accesses are handled transparently by the hardware but incur a 
> performance penalty.

As you say in a reply, may incur. However, shouldn't we also consider
possible ports of SFrame to architectures which don't handle this as
transparently? Off the top of my head I don't, for example, recall
whether RISC-V requires unaligned accesses to be handled transparently
by the hardware.

Jan