Messages in this thread | | | Date | Fri, 22 Dec 2017 16:45:33 +0800 | From | Wei Wang <> | Subject | Re: [PATCH v20 3/7 RESEND] xbitmap: add more operations |
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On 12/21/2017 10:37 PM, Tetsuo Handa wrote: > Matthew Wilcox wrote: >>> +/** >>> + * xb_find_set - find the next set bit in a range of bits >>> + * @xb: the xbitmap to search from >>> + * @offset: the offset in the range to start searching >>> + * @size: the size of the range >>> + * >>> + * Returns: the found bit or, @size if no set bit is found. >>> + */ >>> +unsigned long xb_find_set(struct xb *xb, unsigned long size, >>> + unsigned long offset) >>> +{ >>> + struct radix_tree_root *root = &xb->xbrt; >>> + struct radix_tree_node *node; >>> + void __rcu **slot; >>> + struct ida_bitmap *bitmap; >>> + unsigned long index = offset / IDA_BITMAP_BITS; >>> + unsigned long index_end = size / IDA_BITMAP_BITS; >>> + unsigned long bit = offset % IDA_BITMAP_BITS; >>> + >>> + if (unlikely(offset >= size)) >>> + return size; >>> + >>> + while (index <= index_end) { >>> + unsigned long ret; >>> + unsigned int nbits = size - index * IDA_BITMAP_BITS; >>> + >>> + bitmap = __radix_tree_lookup(root, index, &node, &slot); >>> + >>> + if (!node && !bitmap) >>> + return size; >>> + >>> + if (bitmap) { >>> + if (nbits > IDA_BITMAP_BITS) >>> + nbits = IDA_BITMAP_BITS; >>> + >>> + ret = find_next_bit(bitmap->bitmap, nbits, bit); >>> + if (ret != nbits) >>> + return ret + index * IDA_BITMAP_BITS; >>> + } >>> + bit = 0; >>> + index++; >>> + } >>> + >>> + return size; >>> +} >>> +EXPORT_SYMBOL(xb_find_set); >> This is going to be slower than the implementation I sent yesterday. If I >> call: >> xb_init(xb); >> xb_set_bit(xb, ULONG_MAX); >> xb_find_set(xb, ULONG_MAX, 0); >> >> it's going to call __radix_tree_lookup() 16 quadrillion times. >> My implementation will walk the tree precisely once. >> > Yes. Wei's patch still can not work. > We should start reviewing Matthew's implementation.
It runs without any issue on my machine. I didn't generate an "xbitmap" executable (I just found adding xbitmap executable causes a build error due to a Makefile error), instead, I tested it within "main" and it passed all the tests.
Matthew has implemented a new version, let's start from there.
Best, Wei
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