On Wed, Nov 01, 2023 at 09:02:51PM -1000, Linus Torvalds wrote: > On Wed, 1 Nov 2023 at 10:13, Luis Chamberlain <mcgrof@xxxxxxxxxx> wrote: > > > > The only thing worth highligthing is that gzip moves to use vmalloc() instead of > > kmalloc just as we had a fix for this for zstd on v6.6-rc1. > > Actually, that's almost certainly entirely the wrong thing to do. > > Unless you *know* that the allocation is large, you shouldn't use > vmalloc(). And since kmalloc() has worked fine, you most definitely > don't know that. > > So we have 'kvmalloc()' *exactly* for this reason, which is a "use > kmalloc, unless that is too small, then use vmalloc". > > kmalloc() isn't just about "use physically contiguous allocations". > It's also more memory-efficient, and a *lot* faster than vmalloc(), > which has to play VM tricks. > > So this "just switch to vmalloc()" is entirely wrong. > > Linus I proposed that change mostlfy for consistency with the zstd case, but I haven't experience any issue with gzip compressed modules (that seem to require less memory, even with larger modules). So, yes, it probably makes sense to drop this change for now and I can send another patch to switch to kvmalloc() for all the decompress cases. Thanks, -Andrea
