From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Crawford Subject: Re: Warning about kernel 4.2 performance (revised) Date: Wed, 14 Oct 2015 20:10:20 +0100 Message-ID: <561EA89C.6040203@sat.dundee.ac.uk> References: <20151003085631.02f5b16dfebc7020bf3a1edb@spheresystems.co.uk> <20151004081607.881df23245f969d66eba63b0@spheresystems.co.uk> <5610E4E5.2090802@earthlink.net> <20151004113203.b07e3f6ac66bcba747d75903@spheresystems.co.uk> <56116148.9050608@earthlink.net> <561163AA.6040706@list.ru> <20151005104705.7b2df50cac63a976412ecc22@spheresystems.co.uk> <56125D09.4000108@list.ru> <20151005130317.8c0c970a8953b6792305b5d1@spheresystems.co.uk> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-msdos-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: dosemu Cc: Bart Oldeman Hi Bart, > At least on Westmere+ CPUs (first gen Core i3/i5/i7) KVM can run > "unrestricted guest" mode which behaves like real mode and seems just > as fast as vm86() but it traps less than vm86 so some things that > dosemu depends upon (e.g. that INTs are trapped) do not work. That can > be worked around though with some more coding. In our case the ability to get hardware interrupts routed through to the DOS emulator's code in a prompt manner is VERY important. In fact that is one major reason we have generally not played with the 64-bit version very much in the past. By "prompt" I mean less than 10us or so which was no trouble in the native 286/DOS era, and today should not be a problem given a typical CPU can execute some 30k instructions in that time, but we know that is not how software bloat and indirection go :( Regards, Paul