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| From | Thomas Gleixner <tglx@linutronix.de> |
| Newsgroups | linux.kernel |
| Subject | Re: [patch 2/7] timer: Remove FIFO guarantee |
| Date | Tue, 09 Jun 2015 10:10:03 +0200 |
| Message-ID | <pzmLF-Be-15@gated-at.bofh.it> (permalink) |
| References | <pzkqu-5sk-7@gated-at.bofh.it> |
| X-Original-To | George Spelvin <linux@horizon.com> |
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| X-Original-Date | Tue, 9 Jun 2015 10:05:56 +0200 (CEST) |
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On Tue, 9 Jun 2015, George Spelvin wrote: > Thomas Gleixner wrote: > > > After thinking more about it, I'm even more sure that any code which > > relies on the FIFO "guarantee" is broken today. > > Indeed, I am completely convinced. All I might request is a reassignment > of blame in the commit message. Will do. Thanks for spotting it! > Thank you for your comments on my other blue-sky ideas, too. > > I need to look into why we're using wheels, and what the point is. > How much of an advantage do they have over an efficient priority queue > like a pairing heap? The only reason is performance. The wheel has O(1) insertion and deletion time while heaps and trees usually have O(log(n)). Timer wheel timers are usually timeouts and 99% of them are canceled before expiry. Networking is probably the heaviest use case followed by disk I/O. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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Re: [patch 2/7] timer: Remove FIFO guarantee Thomas Gleixner <tglx@linutronix.de> - 2015-06-09 10:10 +0200
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