Messages in this thread |  | | From | Vincent Mailhol <> | Subject | Re: [PATCH v2 5/6] can: usb: etas_es58X: add support for ETAS ES58X CAN USB interfaces | Date | Fri, 2 Oct 2020 00:56:41 +0900 |
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> > + num_element = > > + es58x_msg_num_element(es58x_dev->dev, > > + bulk_rx_loopback_msg->rx_loopback_msg, > > + msg_len); > > + if (unlikely(num_element <= 0)) > > + return num_element; > > Meta-comment on your use of 'unlikely' everywhere. Please drop it, it's > only to be used if you can actually measure the difference in a > benchmark. You are dealing with USB devices, which are really really > slow here. Also, humans make horrible guessers for this type of thing, > the compiler and CPU can get this right much more often than we can, and > we had the numbers for it (someone measured that 80-90% of our usages of > these markings are actually wrong on modern cpus). > > So just drop them all, it makes the code simpler to read and understand, > and the cpu can actually go faster.
All those branch on which the unlikely() macro were applied were supposed to never been executed under normal circumstances. But I indeed have no benchmark to claim such use.
Thank you for the detailed explanation, makes perfect sense. Each use of the likely()/unlikely() macros will be removed in v3 revision.
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