On Tue, Jan 30, 2024 at 7:56 AM Masahiko Sawada <sawada.m...@gmail.com> wrote: > > On Mon, Jan 29, 2024 at 8:48 PM John Naylor <johncnaylo...@gmail.com> wrote:
> > I meant the macro could probably be > > > > Max(SLAB_DEFAULT_BLOCK_SIZE, (size) * N) > > > > (Right now N=32). I also realize I didn't answer your question earlier > > about block sizes being powers of two. I was talking about PG in > > general -- I was thinking all block sizes were powers of two. If > > that's true, I'm not sure if it's because programmers find the macro > > calculations easy to reason about, or if there was an implementation > > reason for it (e.g. libc behavior). 32*2088 bytes is about 65kB, or > > just above a power of two, so if we did round that up it would be > > 128kB. > > Thank you for your explanation. It might be better to follow other > codes. Does the calculation below make sense to you? > > RT_SIZE_CLASS_ELEM size_class = RT_SIZE_CLASS_INFO[i]; > Size inner_blocksize = SLAB_DEFAULT_BLOCK_SIZE; > while (inner_blocksize < 32 * size_class.allocsize) > inner_blocksize <<= 1; It does make sense, but we can do it more simply: Max(SLAB_DEFAULT_BLOCK_SIZE, pg_nextpower2_32(size * 32))
