On Fri, Feb 18, 2022 at 04:10:28PM +0000, David Laight wrote: > From: Hyeonggon Yoo > > Sent: 18 February 2022 10:13 > ... > > I think SLUB can be memory-efficient as SLOB. > > Is SLOB (Address-Ordered next^Wfirst fit) stronger to fragmentation than SLUB? > > Dunno, but I had to patch the vxworks malloc to use 'best fit' > because 'first fit' based on a fifo free list was really horrid. > > I can't imagine an address ordered 'first fit' really being that much better. > > There are probably a lot more allocs and frees than the kernel used to have. > > Also isn't the performance of a 'first fit' going to get horrid > when there are a lot of small items on the free list. SLOB is focused on low memory usage, at the cost of poor performance. Its speed is not a concern. I think Address-Ordered sequential fit method pretty well in terms of low memory usage. And I think SLUB may replace SLOB, but we need to sure SLUB is absolute winner.. I wonder How slab maintainers think? > > Does SLUB split pages into 3s and 5s (on cache lime boundaries) > as well as powers of 2? > SLUB/SLAB use different strategy than SLOB, for better allocation performance. It's variant of segregated storage method. SLUB/SLAB both creates dedicated "caches" for each type of object. for example, on my system, there are slab cache for dentry(192), filp(256), fs_cache(64) ... etc. Objects that has different types are by default managed by different cache, which holds manages of pages. slab caches can be merged for better cacheline utilization. SLUB/SLAB also creates global kmalloc caches at boot time for power of 2 objects and (128, 256, 512, 1K, 2K, 4K, 8K on my system). Thanks, Hyeonggon. > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) >
