On Wed, Dec 15, 2021 at 11:10:06AM +0100, Vlastimil Babka wrote: > On 12/15/21 07:29, Hyeonggon Yoo wrote: > > On Tue, Dec 14, 2021 at 06:24:58PM +0100, Vlastimil Babka wrote: > >> On 12/10/21 13:06, Christoph Lameter wrote: > >> > On Fri, 10 Dec 2021, Hyeonggon Yoo wrote: > >> > > >> >> > > (But I still have doubt if we can run linux on machines like that.) > >> >> > > >> >> > I sent you a series of articles about making Linux run in 1MB. > >> >> > >> >> After some time playing with the size of kernel, > >> >> I was able to run linux in 6.6MiB of RAM. and the SLOB used > >> >> around 300KiB of memory. > >> > > >> > What is the minimal size you need for SLUB? > >> > > > > I don't know why Christoph's mail is not in my mailbox. maybe I deleted it > > by mistake or I'm not cc-ed. > > > > Anyway, I tried to measure this again with SLUB and SLOB. > > > > SLUB uses few hundreds of bytes than SLOB. > > > > There isn't much difference in 'Memory required to boot'. > > (interestingly SLUB requires less) > > > > 'Memory required to boot' is measured by reducing memory > > until it says 'System is deadlocked on memory'. I don't know > > exact reason why they differ. > > > > Note that the configuration is based on tinyconfig and > > I added initramfs support + tty layer (+ uart driver) + procfs support, > > + ELF binary support + etc. > > > > there isn't even block layer, but it's good starting point to see > > what happens in small system. > > > > SLOB: > > > > Memory required to boot: 6950K > > > > Slab: 368 kB > > > > SLUB: > > Memory required to boot: 6800K > > > > Slab: 552 kB > > > > SLUB with slab merging: > > > > Slab: 536 kB > > 168kB different on a system with less than 8MB memory looks rather > significant to me to simply delete SLOB, I'm afraid. Just FYI... Some experiment based on v5.17-rc3: SLOB: Slab: 388 kB SLUB: Slab: 540 kB (+152kb) SLUB with s->min_partial = 0: Slab: 452 kB (+64kb) SLUB with s->min_partial = 0 && slub_max_order = 0: Slab: 436 kB (+48kb) SLUB with s->min_partial = 0 && slub_max_order = 0 + merging slabs crazily (just ignore SLAB_NEVER_MERGE/SLAB_MERGE_SAME): Slab: 408 kB (+20kb) Decreasing further seem to be hard and I guess +20kb are due to partial slabs. I think SLUB can be memory-efficient as SLOB. Is SLOB (Address-Ordered next fit) stronger to fragmentation than SLUB?
