Date: Sun, 21 Aug 2016 08:55:11 -0500 From: Karl Denninger <karl@denninger.net> To: freebsd-fs@freebsd.org Subject: Re: ZFS ARC under memory pressure Message-ID: <73545a4b-fafc-f623-a8f5-cfcd3d8a2bd7@denninger.net> In-Reply-To: <20160821082842.GR83214@kib.kiev.ua> References: <20160816193416.GM8192@zxy.spb.ru> <8dbf2a3a-da64-f7f8-5463-bfa23462446e@FreeBSD.org> <20160818202657.GS8192@zxy.spb.ru> <c3bc6c5a-961c-e3a4-2302-f0f7417bc34f@denninger.net> <20160819201840.GA12519@zxy.spb.ru> <bcb14d0b-bd6d-cb93-ea71-3656cfce8b3b@denninger.net> <20160820152225.GP83214@kib.kiev.ua> <97f166f0-4d47-d5a3-ecb3-d15f1ecf9c1f@denninger.net> <20160821082842.GR83214@kib.kiev.ua>
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This is a cryptographically signed message in MIME format. --------------ms040408040108020304040707 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 8/21/2016 03:28, Konstantin Belousov wrote: > On Sat, Aug 20, 2016 at 11:08:44AM -0500, Karl Denninger wrote: >> If you are talking about the case of an executable in which part of th= e >> text is evicted you are correct, however, you are still choosing in th= at >> instance to evict a page for which there will likely be a future deman= d >> and thus require an I/O (should that executable come back up for >> execution) as opposed to one for which you have no idea how likely >> demand for same will be (a data page in the ARC.) > No, I am not talking about only text segments. > Any clean page can be reused after unmapping. And this accounts for pages being evicted to the swap..... how?=20 (Obviously they're not simply unmapped, and thus were not "clean" when targeted by the VM) >> Since the VM has no means of "coloring" the ARC (as it is opaque other= >> than the consumption of system memory to the VM) as to how "useful" >> (e.g. how often used, etc) a particular data item in the ARC is, it ha= s >> no information available on which to decide. However, the fact that a= n >> executing process is in some sort of waiting state still likely trumps= >> an ARC data page in terms of likelihood of future access. > Buffer cache behaves exactly the same, since access references are not > counted for the pages constituing buffers. It is always amusing when I am told how things are supposed to occur (and thus assumptions that were made when writing code) when I have spent countless hours observing how they actually do behave and writing code to mitigate the very behavior that is claimed to not happen. I should have something for 11-MostlyStable on the original PR's thread in a couple of weeks, assuming I manage to complete what I'm working on right now on-schedule. --=20 Karl Denninger karl@denninger.net <mailto:karl@denninger.net> /The Market Ticker/ /[S/MIME encrypted email preferred]/ --------------ms040408040108020304040707 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC Bl8wggZbMIIEQ6ADAgECAgEpMA0GCSqGSIb3DQEBCwUAMIGQMQswCQYDVQQGEwJVUzEQMA4G A1UECBMHRmxvcmlkYTESMBAGA1UEBxMJTmljZXZpbGxlMRkwFwYDVQQKExBDdWRhIFN5c3Rl bXMgTExDMRwwGgYDVQQDExNDdWRhIFN5c3RlbXMgTExDIENBMSIwIAYJKoZIhvcNAQkBFhND dWRhIFN5c3RlbXMgTExDIENBMB4XDTE1MDQyMTAyMjE1OVoXDTIwMDQxOTAyMjE1OVowWjEL MAkGA1UEBhMCVVMxEDAOBgNVBAgTB0Zsb3JpZGExGTAXBgNVBAoTEEN1ZGEgU3lzdGVtcyBM TEMxHjAcBgNVBAMTFUthcmwgRGVubmluZ2VyIChPQ1NQKTCCAiIwDQYJKoZIhvcNAQEBBQAD ggIPADCCAgoCggIBALmEWPhAdphrWd4K5VTvE5pxL3blRQPyGF3ApjUjgtavqU1Y8pbI3Byg XDj2/Uz9Si8XVj/kNbKEjkRh5SsNvx3Fc0oQ1uVjyCq7zC/kctF7yLzQbvWnU4grAPZ3IuAp 3/fFxIVaXpxEdKmyZAVDhk9az+IgHH43rdJRIMzxJ5vqQMb+n2EjadVqiGPbtG9aZEImlq7f IYDTnKyToi23PAnkPwwT+q1IkI2DTvf2jzWrhLR5DTX0fUYC0nxlHWbjgpiapyJWtR7K2YQO aevQb/3vN9gSojT2h+cBem7QIj6U69rEYcEDvPyCMXEV9VcXdcmW42LSRsPvZcBHFkWAJqMZ Myiz4kumaP+s+cIDaXitR/szoqDKGSHM4CPAZV9Yh8asvxQL5uDxz5wvLPgS5yS8K/o7zDR5 vNkMCyfYQuR6PAJxVOk5Arqvj9lfP3JSVapwbr01CoWDBkpuJlKfpQIEeC/pcCBKknllbMYq yHBO2TipLyO5Ocd1nhN/nOsO+C+j31lQHfOMRZaPQykXVPWG5BbhWT7ttX4vy5hOW6yJgeT/ o3apynlp1cEavkQRS8uJHoQszF6KIrQMID/JfySWvVQ4ksnfzwB2lRomrdrwnQ4eG/HBS+0l eozwOJNDIBlAP+hLe8A5oWZgooIIK/SulUAsfI6Sgd8dTZTTYmlhAgMBAAGjgfQwgfEwNwYI KwYBBQUHAQEEKzApMCcGCCsGAQUFBzABhhtodHRwOi8vY3VkYXN5c3RlbXMubmV0Ojg4ODgw CQYDVR0TBAIwADARBglghkgBhvhCAQEEBAMCBaAwCwYDVR0PBAQDAgXgMCwGCWCGSAGG+EIB DQQfFh1PcGVuU1NMIEdlbmVyYXRlZCBDZXJ0aWZpY2F0ZTAdBgNVHQ4EFgQUxRyULenJaFwX RtT79aNmIB/u5VkwHwYDVR0jBBgwFoAUJHGbnYV9/N3dvbDKkpQDofrTbTUwHQYDVR0RBBYw FIESa2FybEBkZW5uaW5nZXIubmV0MA0GCSqGSIb3DQEBCwUAA4ICAQBPf3cYtmKowmGIYsm6 eBinJu7QVWvxi1vqnBz3KE+HapqoIZS8/PolB/hwiY0UAE1RsjBJ7yEjihVRwummSBvkoOyf G30uPn4yg4vbJkR9lTz8d21fPshWETa6DBh2jx2Qf13LZpr3Pj2fTtlu6xMYKzg7cSDgd2bO sJGH/rcvva9Spkx5Vfq0RyOrYph9boshRN3D4tbWgBAcX9POdXCVfJONDxhfBuPHsJ6vEmPb An+XL5Yl26XYFPiODQ+Qbk44Ot1kt9s7oS3dVUrh92Qv0G3J3DF+Vt6C15nED+f+bk4gScu+ JHT7RjEmfa18GT8DcT//D1zEke1Ymhb41JH+GyZchDRWtjxsS5OBFMzrju7d264zJUFtX7iJ 3xvpKN7VcZKNtB6dLShj3v/XDsQVQWXmR/1YKWZ93C3LpRs2Y5nYdn6gEOpL/WfQFThtfnat HNc7fNs5vjotaYpBl5H8+VCautKbGOs219uQbhGZLYTv6okuKcY8W+4EJEtK0xB08vqr9Jd0 FS9MGjQE++GWo+5eQxFt6nUENHbVYnsr6bYPQsZH0CRNycgTG9MwY/UIXOf4W034UpR82TBG 1LiMsYfb8ahQJhs3wdf1nzipIjRwoZKT1vGXh/cj3gwSr64GfenURBxaFZA5O1acOZUjPrRT n3ci4McYW/0WVVA3lDGCBRMwggUPAgEBMIGWMIGQMQswCQYDVQQGEwJVUzEQMA4GA1UECBMH RmxvcmlkYTESMBAGA1UEBxMJTmljZXZpbGxlMRkwFwYDVQQKExBDdWRhIFN5c3RlbXMgTExD MRwwGgYDVQQDExNDdWRhIFN5c3RlbXMgTExDIENBMSIwIAYJKoZIhvcNAQkBFhNDdWRhIFN5 c3RlbXMgTExDIENBAgEpMA0GCWCGSAFlAwQCAwUAoIICTTAYBgkqhkiG9w0BCQMxCwYJKoZI hvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xNjA4MjExMzU1MTFaME8GCSqGSIb3DQEJBDFCBEC9 pc0+jrZ0NX1tcdjEiw11v/KjDQbuGvjFC7TC4kl/8/Y3k5ByJDgIttFRurk1aLBW6bFxDm6l g9ZN44SP8gRCMGwGCSqGSIb3DQEJDzFfMF0wCwYJYIZIAWUDBAEqMAsGCWCGSAFlAwQBAjAK BggqhkiG9w0DBzAOBggqhkiG9w0DAgICAIAwDQYIKoZIhvcNAwICAUAwBwYFKw4DAgcwDQYI KoZIhvcNAwICASgwgacGCSsGAQQBgjcQBDGBmTCBljCBkDELMAkGA1UEBhMCVVMxEDAOBgNV BAgTB0Zsb3JpZGExEjAQBgNVBAcTCU5pY2V2aWxsZTEZMBcGA1UEChMQQ3VkYSBTeXN0ZW1z IExMQzEcMBoGA1UEAxMTQ3VkYSBTeXN0ZW1zIExMQyBDQTEiMCAGCSqGSIb3DQEJARYTQ3Vk YSBTeXN0ZW1zIExMQyBDQQIBKTCBqQYLKoZIhvcNAQkQAgsxgZmggZYwgZAxCzAJBgNVBAYT AlVTMRAwDgYDVQQIEwdGbG9yaWRhMRIwEAYDVQQHEwlOaWNldmlsbGUxGTAXBgNVBAoTEEN1 ZGEgU3lzdGVtcyBMTEMxHDAaBgNVBAMTE0N1ZGEgU3lzdGVtcyBMTEMgQ0ExIjAgBgkqhkiG 9w0BCQEWE0N1ZGEgU3lzdGVtcyBMTEMgQ0ECASkwDQYJKoZIhvcNAQEBBQAEggIADmOtAIUa 0iN5NYqGUe8eRO77avZpPHDaq7yLkFbhefpDQzRyjlqd1S8wuQikiNkXdxa8qi6ZpVBXZVvM 1hs/CtmArnxF/De3uCf2NFCSrqPAUtSfXeM7TzVLs8rtoJHnh27H706RB9BkayJXPH4GSlg1 DcSmHiGg0wPbHVN5xTirvIbUIVi09aWNnZL31wJ+rRP+zLHEVifvLb9Oxo1iODRTErO0Pi6K Odr20I2lZF/ULgGa6KuA9PG8spadfZmuDilg8WCXYdFicRPky1ldpIfVVwSEQwSUiMyzu7aF kbpYbplBvMnVu704K+mvrUJYVhHyG9TbXIj/34ICItPQFG278FuOiVVHEA1+dS7KQyOWribi 5XYg6i7EwcPw3rfZrblsOW5TDZfX+ktv57HUCBvwuKGjRHbm/MNEfRQc4npSku2aO2OmoI+K 4+zEcf6SEaJVwuEvJl2e9yb/yrDgf0zH7ESIubekgVeyzeheJ7kkFcevtJc4vsnIwXgSqwWU gsCWmnSTDdEibLq6nOAt4HrmyMd8LJ0sv1SrepoK0hoviup+NiYlL5Ytwt+L7wPW+TysIZ6t Yqu2LG7+hH6R0SLvcBRU3mMhtLvXybz39qYVFNZ+jMQOLCxkbqVi3635UchGWnA0VA7rzaRL xX0zoChmSsJDUPQED89Z6phD600AAAAAAAA= --------------ms040408040108020304040707--
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