GFP_ATOMIC & GFP_KERNEL kmalloc& vmalloc-优快云博客

本文深入探讨了Linux内核中GFP_ATOMIC和GFP_KERNEL内存分配标志的区别，阐述了它们在不同场景下的应用及优劣，特别强调了在中断处理中的使用。同时指出，在某些情况下使用GFP_KERNEL可能比GFP_ATOMIC更合适。

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GFP_ATOMIC means roughly "make the allocation operation atomic". This
means that the kernel will try to find the memory using a pile of free
memory set aside for urgent allocation. If that pile doesn't have
enough free pages, the operation will fail. This flag is useful for
allocation within interrupt handlers.

GFP_KERNEL will try a little harder to find memory. There's a
possibility that the call to kmalloc() will sleep while the kernel is
trying to find memory (thus making it unsuitable for interrupt
handlers). It's much more rare for an allocation with GFP_KERNEL to
fail than with GFP_ATOMIC.

In all cases, kmalloc() should only be used allocating small amounts of
memory (a few kb). vmalloc() is better for larger amounts.

Also note that in lab 1 and lab 2, it would have been arguably better to
use GFP_KERNEL instead of GFP_ATOMIC. GFP_ATOMIC should be saved for
those instances in which a sleep would be totally unacceptable.

This is a fuzzy issue though...there's no absolute right or wrong
answer.