Date: Thu, 21 Feb 2002 17:22:17 -0800 From: Lars Eggert <larse@ISI.EDU> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Jeff Roberson <jroberson@chesapeake.net>, Julian Elischer <julian@elischer.org>, arch@FreeBSD.ORG Subject: Re: Prioritized bio patches. (Updated patch) Message-ID: <3C759D49.2070003@isi.edu> References: <20020219194142.M12686-100000@mail.chesapeake.net> <200202220106.g1M168p12213@apollo.backplane.com>
index | next in thread | previous in thread | raw e-mail
[-- Attachment #1 --] Matthew Dillon wrote: > Priority inversion can be a serious problem, especially in more > heavily loaded systems. I don't think it would be safe to commit > a bio priority mechanism without dealing with the problem. > > Another possibility is to guarentee that the I/O request will > eventually go out by slowly bumping up its priority in the queue, > so it doesn't get stuck indefinintely. I'm looking at something similar as part of my thesis. The idea is to provide a way to use idle resource capacity (on all major resources) without interfering with regular processing. (The second part of my thesis is using this free capacity speculatively to improve performance. In some sense, it's the OS equivalent of speculative execution on CPUs.) For that, you'd want starvation and strict priorities. Priority inversion is avoided by having regular processes issue only regular-class resource requests, and idle-time processes only issue low-priority requests. I'm interested in Jeff's patches, and just started to look if I can port them to -STABLE. (Can't move to -CURRENT because I depend on ALTQ for part of my network stack idle-time hacks.) Lars -- Lars Eggert <larse@isi.edu> Information Sciences Institute http://www.isi.edu/larse/ University of Southern California [-- Attachment #2 --] 0 *H 01 0 + 0 *H 00 G0 *H 01 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.300 010824164000Z 020824164000Z0T10 UEggert1 0 U*Lars10U Lars Eggert1 0 *H larse@isi.edu00 *H 0 |\Pw v~~ FDooӦA\- Cˀ4.)&{肋 ,z (ܷر߈T7_'txGH^tt/ҹB8%t<#ֲN V0T0*+e!0 00L2uMyffBNUbNJJcdZ2s0U 0 larse@isi.edu0 U 0 0 *H aJPMՒ ]cѭC+kS+wZ1gY",YT41 j 6:~℩ D~Kؚl=u(ՎM?cF7@}T00 G0 *H 01 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.300 010824164000Z 020824164000Z0T10 UEggert1 0 U*Lars10U Lars Eggert1 0 *H larse@isi.edu00 *H 0 |\Pw v~~ FDooӦA\- Cˀ4.)&{肋 ,z (ܷر߈T7_'txGH^tt/ҹB8%t<#ֲN V0T0*+e!0 00L2uMyffBNUbNJJcdZ2s0U 0 larse@isi.edu0 U 0 0 *H aJPMՒ ]cѭC+kS+wZ1gY",YT41 j 6:~℩ D~Kؚl=u(ՎM?cF7@}T0)0 0 *H 01 0 UZA10U Western Cape10U Cape Town10U Thawte Consulting1(0&U Certification Services Division1$0"UThawte Personal Freemail CA1+0) *H personal-freemail@thawte.com0 000830000000Z 020829235959Z01 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.3000 *H 0 32c %E>nx'gڈD)c5*mp<ܮto034qmOe KaU5u'rװ |CBPQ<9TIf - ki N0L0)U "0 0 10UPrivateLabel1-2970U 0 0 U 0 *H so&e4KYbDI j&*b ct mSK8P:l4撜n# KrgPo.X PW Ո9[9}4%MjÑ/<RbH10001 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.30G0 + a0 *H 1 *H 0 *H 1 020222012217Z0# *H 1z(wuAk0R *H 1E0C0 *H 0*H 0 *H @0+0 *H (0 *H 101 0 UZA10U Western Cape10U Cape Town10 U Thawte1 0U Certificate Services1(0&U Personal Freemail RSA 2000.8.30G0 *H @03qk沈 d'5fN,64x|~_1 c8 [&D)sQ"#-x _8Lʍ04 `.,JZ?:S ڑ& l)5_ Dzɘhome | help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3C759D49.2070003>