On Fri, 28 Feb 2025 at 06:24, Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx> wrote: > > On (25/02/26 14:00), David Sterba wrote: > > What strikes me as alarming that you insert about 20 branches into a > > realtime compression algorithm, where everything is basically a hot > > path. Branches that almost never happen, and never if the output buffer > > is big enough. > > > > Please drop the patch. > > David, just for educational purposes, there's only safe variant of lzo > decompression, which seems to be doing a lot of NEED_OP (HAVE_OP) adding > branches and so on, basically what Herbert is adding to the compression > path. So my question is - why NEED_OP (if (!HAVE_OP(x)) goto output_overrun) > is a no go for compression, but appears to be fine for decompression? > Because compression has a bounded worst case (compressing data with LZO can actually increase the size but only by a limited amount), whereas decompressing a small input could produce gigabytes of output.
