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>
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This is a cryptographically signed message in MIME format. --------------ms010607060108030403080906 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit 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 --------------ms010607060108030403080906 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIInzCC ArUwggIeoAMCAQICAwWBRzANBgkqhkiG9w0BAQIFADCBkjELMAkGA1UEBhMCWkExFTATBgNV BAgTDFdlc3Rlcm4gQ2FwZTESMBAGA1UEBxMJQ2FwZSBUb3duMQ8wDQYDVQQKEwZUaGF3dGUx HTAbBgNVBAsTFENlcnRpZmljYXRlIFNlcnZpY2VzMSgwJgYDVQQDEx9QZXJzb25hbCBGcmVl bWFpbCBSU0EgMjAwMC44LjMwMB4XDTAxMDgyNDE2NDAwMFoXDTAyMDgyNDE2NDAwMFowVDEP MA0GA1UEBBMGRWdnZXJ0MQ0wCwYDVQQqEwRMYXJzMRQwEgYDVQQDEwtMYXJzIEVnZ2VydDEc MBoGCSqGSIb3DQEJARYNbGFyc2VAaXNpLmVkdTCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkC gYEA0AvLBsD78nxcUHeHkaMgl3b4qYPnfgbf8Lh+HQP8RgGMRG/Yb+vTpkGezlwt9pkJxiD1 1uZDy4CNNJUu3gKxKSb+zRV70O+lkwwftuHoLHoH4xwo3LcQ2LGDpd+I95tUN4dfJ3TmeEcU SF50dC/SuUI4w8AlhXQ8IxrhgdayTpECAwEAAaNWMFQwKgYFK2UBBAEEITAfAgEAMBowGAIB BAQTTDJ1TXlmZkJOVWJOSkpjZFoyczAYBgNVHREEETAPgQ1sYXJzZUBpc2kuZWR1MAwGA1Ud EwEB/wQCMAAwDQYJKoZIhvcNAQECBQADgYEAheZhn0pQA8zI7U2K1ZIAl11j0a1DKxnp3GtT vOUrGRB3WvYxidvdZ1kizhEsWeXU81TkNDH0DaRqtOEeu6Q2OhB+jeKEqY7IDAJE4/fI0e+d 6PnG1hd+vEvYmsKHkmzBhPc94XUOKNWO+qVNP2NGyNI3QIDy5wX4fdcOo1S34r4wggK1MIIC HqADAgECAgMFgUcwDQYJKoZIhvcNAQECBQAwgZIxCzAJBgNVBAYTAlpBMRUwEwYDVQQIEwxX ZXN0ZXJuIENhcGUxEjAQBgNVBAcTCUNhcGUgVG93bjEPMA0GA1UEChMGVGhhd3RlMR0wGwYD VQQLExRDZXJ0aWZpY2F0ZSBTZXJ2aWNlczEoMCYGA1UEAxMfUGVyc29uYWwgRnJlZW1haWwg UlNBIDIwMDAuOC4zMDAeFw0wMTA4MjQxNjQwMDBaFw0wMjA4MjQxNjQwMDBaMFQxDzANBgNV BAQTBkVnZ2VydDENMAsGA1UEKhMETGFyczEUMBIGA1UEAxMLTGFycyBFZ2dlcnQxHDAaBgkq hkiG9w0BCQEWDWxhcnNlQGlzaS5lZHUwgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBANAL ywbA+/J8XFB3h5GjIJd2+KmD534G3/C4fh0D/EYBjERv2G/r06ZBns5cLfaZCcYg9dbmQ8uA jTSVLt4CsSkm/s0Ve9DvpZMMH7bh6Cx6B+McKNy3ENixg6XfiPebVDeHXyd05nhHFEhedHQv 0rlCOMPAJYV0PCMa4YHWsk6RAgMBAAGjVjBUMCoGBStlAQQBBCEwHwIBADAaMBgCAQQEE0wy dU15ZmZCTlViTkpKY2RaMnMwGAYDVR0RBBEwD4ENbGFyc2VAaXNpLmVkdTAMBgNVHRMBAf8E AjAAMA0GCSqGSIb3DQEBAgUAA4GBAIXmYZ9KUAPMyO1NitWSAJddY9GtQysZ6dxrU7zlKxkQ d1r2MYnb3WdZIs4RLFnl1PNU5DQx9A2karThHrukNjoQfo3ihKmOyAwCROP3yNHvnej5xtYX frxL2JrCh5JswYT3PeF1DijVjvqlTT9jRsjSN0CA8ucF+H3XDqNUt+K+MIIDKTCCApKgAwIB AgIBDDANBgkqhkiG9w0BAQQFADCB0TELMAkGA1UEBhMCWkExFTATBgNVBAgTDFdlc3Rlcm4g Q2FwZTESMBAGA1UEBxMJQ2FwZSBUb3duMRowGAYDVQQKExFUaGF3dGUgQ29uc3VsdGluZzEo MCYGA1UECxMfQ2VydGlmaWNhdGlvbiBTZXJ2aWNlcyBEaXZpc2lvbjEkMCIGA1UEAxMbVGhh d3RlIFBlcnNvbmFsIEZyZWVtYWlsIENBMSswKQYJKoZIhvcNAQkBFhxwZXJzb25hbC1mcmVl bWFpbEB0aGF3dGUuY29tMB4XDTAwMDgzMDAwMDAwMFoXDTAyMDgyOTIzNTk1OVowgZIxCzAJ BgNVBAYTAlpBMRUwEwYDVQQIEwxXZXN0ZXJuIENhcGUxEjAQBgNVBAcTCUNhcGUgVG93bjEP MA0GA1UEChMGVGhhd3RlMR0wGwYDVQQLExRDZXJ0aWZpY2F0ZSBTZXJ2aWNlczEoMCYGA1UE AxMfUGVyc29uYWwgRnJlZW1haWwgUlNBIDIwMDAuOC4zMDCBnzANBgkqhkiG9w0BAQEFAAOB jQAwgYkCgYEA3jMypmPHCSVFPtJueCdngcXaiBmClw7jRCmKYzUqbXA8+tyu9+50bzC8M5B/ +TRxoKNtmPHDT6Jl2w36S/HW3WGl+YXNVZo1Gp2Sdagnrthy+boC9tewkd4c6avgGAOofENC UFGHgzzwObSbVIoTh/+zm51JZgAtCYnslGvpoWkCAwEAAaNOMEwwKQYDVR0RBCIwIKQeMBwx GjAYBgNVBAMTEVByaXZhdGVMYWJlbDEtMjk3MBIGA1UdEwEB/wQIMAYBAf8CAQAwCwYDVR0P BAQDAgEGMA0GCSqGSIb3DQEBBAUAA4GBAHMbbyZli/8VNEtZYortRL5Jx+gNu4+5DWomKmKE H7iHY3QcbbfPGlORS+HN5jjZ7VD0Omw0kqzmkpxuwSMBwgmn70uuct0GZ/VQby5YuLYLwVBX tewc1+8XttWIm7eiiBrtOVs5fTT8tpYYJU1q9J3Fw5EvqZa4BTxS/N3pYgNIMYICpjCCAqIC AQEwgZowgZIxCzAJBgNVBAYTAlpBMRUwEwYDVQQIEwxXZXN0ZXJuIENhcGUxEjAQBgNVBAcT CUNhcGUgVG93bjEPMA0GA1UEChMGVGhhd3RlMR0wGwYDVQQLExRDZXJ0aWZpY2F0ZSBTZXJ2 aWNlczEoMCYGA1UEAxMfUGVyc29uYWwgRnJlZW1haWwgUlNBIDIwMDAuOC4zMAIDBYFHMAkG BSsOAwIaBQCgggFhMBgGCSqGSIb3DQEJAzELBgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8X DTAyMDIyMjAxMjIxN1owIwYJKoZIhvcNAQkEMRYEFIB6jbyi8gHpKN93dcGeQYf/jWvhMFIG CSqGSIb3DQEJDzFFMEMwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMC AgFAMAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGtBgsqhkiG9w0BCRACCzGBnaCBmjCBkjEL MAkGA1UEBhMCWkExFTATBgNVBAgTDFdlc3Rlcm4gQ2FwZTESMBAGA1UEBxMJQ2FwZSBUb3du MQ8wDQYDVQQKEwZUaGF3dGUxHTAbBgNVBAsTFENlcnRpZmljYXRlIFNlcnZpY2VzMSgwJgYD VQQDEx9QZXJzb25hbCBGcmVlbWFpbCBSU0EgMjAwMC44LjMwAgMFgUcwDQYJKoZIhvcNAQEB BQAEgYAAmfBAzjAzv3GKa5/E64zmsoi7Cr5kgt3nJzXIZk4sNjSneBt8fofGX38xH2M4lu0M olsm7kTHKXNRIiPdAy14EAsR0184TMqNhfL4MMk0kQ4cf2DXLiyQG0qNWj86Ux/nEoKZ2pGI Jq6IDg3rbLKhqLopNQ5f8g3Hsqz6ucmY/QAAAAAAAA== --------------ms010607060108030403080906-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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