Date: Mon, 18 Feb 2002 19:02:24 -0800 (PST) From: Julian Elischer <julian@elischer.org> To: Jeff Roberson <jroberson@chesapeake.net> Cc: arch@freebsd.org Subject: Re: Prioritized bio patches. Message-ID: <Pine.BSF.4.21.0202181900270.53728-100000@InterJet.elischer.org> In-Reply-To: <20020218214128.C12686-100000@mail.chesapeake.net>
next in thread | previous in thread | raw e-mail | index | archive | help
this is kind of cool Can you give any figures showing realtive effects on (say) buildworld time when there is NICE work also on the system? (I guess you must have doen it for a reason, so maybe you can give us some examples of the result) regards, julian On Mon, 18 Feb 2002, Jeff Roberson wrote: > I have developed an extension to the bio queue interface to support > priorities. It may be useful in place of the nice value related sleep > that is currently in bioqdisksort. There are 6 queues in each bio queue > head. The first is the default sorted queue. It is used if the bio > priority (bio_prio) is BIO_PRIO_DEFAULT. Then there are 5 unsorted queues > for use with different nice levels. > > The priority is automatically picked at insert time based on the process > nice value. Un-nice processes still use the default IO queue to prevent > starvation. The lower priority IO is not sorted because it may be > interrupted at any time by higher priority io, thus defeating the sort. > This also saves a bit of structure bloat and processing time. > > The main advantage over the current solution is that, if the system has > spare IO cycles, nice processes can run at full speed. Also, this was > implemented in such a way that it is completely transparent to users of > the bioq interfaces. Since cam keeps a deep queue of IOs it may want to > adjust it's priorities for the IO as well. This would prevent a possible > delay for high priority IO while cam works through a queue full of low > priority IO. As it is though the response time should be reasonable. > > This patch does not introduce any higher priority levels. It would be > easy to do, but I don't see any demand for it right now. The patch is > available at http://www.chesapeake.net/~jroberson/prio.patch > > Thanks, > Jeff > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-arch" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.BSF.4.21.0202181900270.53728-100000>