Date: Sun, 27 Mar 2005 12:36:45 +0200 From: Anthony Atkielski <atkielski.anthony@wanadoo.fr> To: freebsd-questions@freebsd.org Subject: Re: hyper threading. Message-ID: <467157066.20050327123645@wanadoo.fr> In-Reply-To: <8C700841A4F8661-A38-3B468@mblk-r33.sysops.aol.com> References: <c6ef380c050326061976f164b@mail.gmail.com> <1641928994.20050326192811@wanadoo.fr> <8C700529A2DFD74-A44-3A157@mblk-d34.sysops.aol.com> <439876144.20050326220638@wanadoo.fr> <8C7006AE7E80573-FAC-3B652@mblk-r28.sysops.aol.com> <49251524.20050326234521@wanadoo.fr> <8C7007D5D4D30D2-A38-3B313@mblk-r33.sysops.aol.com> <42460B1C.1050008@cloudview.com> <8C700841A4F8661-A38-3B468@mblk-r33.sysops.aol.com>
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em1897@aol.com writes: > When you get your machine running without a kernel > let me know. The kernel is the key to the O/S. If you > don't need networking and don't have many interrupts, > then it probably doesnt matter that much. The kernel represents only a small part of total system utilization and throughput. Even if everything is single-threaded through the kernel, you can still get performance benefits from multiple processors, because they can run userland processes in parallel. If total system load is 5% kernel and 80% userland in a UP environment, and moving to a MP environment doubles kernel overhead, total system load has still increased by only 5%. In general, many things must be single-threaded through the kernel because of the need for proper synchronization. Thus, the kernel always shows more negative effects from MP than the system as a whole, but since it is so small in the overall picture, MP still improves global performance. -- Anthony
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