Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH] ext4: convert to DIV_ROUND_UP() in mpage_process_page_bufs() | Date | Mon, 13 Mar 2023 09:25:20 +0000 |
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... > On 32-bit platforms --- i386 in particular --- the 64-bit division > results in an out-of-line call to a helper function that is not > supplied in the kernel compilation environment, so not only is it > slower, it Just Doesn't Work.
Even on some 64-bit systems a 64bit divide can be significantly slower than a 32-bit divide - even with the same arguments. IIRC Intel x86-64 a 64-bit divide (128-bit dividend) is about twice the clocks of a 32-bit one. On AMD cpu they are much the same.
David
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