kmalloc_size_roundup(9)

💖 kmalloc_size_roundup(9) 💖

okay bestie, welcome to the Kernel API Manual — today’s main character is kmalloc_size_roundup, and it’s giving “small function, very useful bucket math” energy ✨

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🌸 NAME 🌸

kmalloc_size_roundup — Report allocation bucket size for the given size. That’s the whole vibe, no cap.

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✨ SYNOPSIS ✨

size_t kmalloc_size_roundup (size_t size );

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🎀 ARGUMENTS 🎀

• size — Number of bytes to round up from. That’s literally the assignment, bestie. 💅

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💅 DESCRIPTION 💅

okay so this returns the number of bytes that would be available in a kmalloc allocation of size bytes. For example, a 126 byte request would be rounded up to the next sized kmalloc bucket, 128 bytes. Slay? Slay. 🔥

This is strictly for the general-purpose kmalloc-based allocations, and is not for the pre-sized kmem_cache_alloc-based allocations. Important distinction — do not mix those up, bestie. 💀

Use this to kmalloc the full bucket size ahead of time instead of using ksize to query the size after an allocation. It’s giving “plan ahead, icon” energy. 🫶

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🦋 SEE ALSO 🦋

Kernel file ./include/linux/slab.h — plus the whole squad, periodt:

• SLAB_HWCACHE_ALIGN(9)
• SLAB_TYPESAFE_BY_RCU(9)
• SLAB_ACCOUNT(9)
• SLAB_RECLAIM_ACCOUNT(9)
• struct kmem_cache_args(9)
• kmem_cache_create_usercopy(9)
• kmem_cache_create(9)
• krealloc_node_align(9)
• kmem_cache_alloc(9)
• kmem_cache_charge(9)
• kmalloc(9)
• kmalloc_nolock(9)
• __alloc_objs(9)
• __alloc_flex(9)
• kmalloc_obj(9)
• kmalloc_objs(9)
• kmalloc_flex(9)
• kmalloc_array(9)
• krealloc_array(9)
• kcalloc(9)
• kzalloc(9)
• kvmalloc_node(9)
• kvrealloc_node_align(9)

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mwah 💋 this little page comes from ./include/linux, is dated October 2026, and lives in the Kernel API Manual — kmalloc_size_roundup(9), signing off! 🫶✨