From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751619AbbINSiG (ORCPT ); Mon, 14 Sep 2015 14:38:06 -0400 Received: from mail-ig0-f180.google.com ([209.85.213.180]:33163 "EHLO mail-ig0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750951AbbINSiF (ORCPT ); Mon, 14 Sep 2015 14:38:05 -0400 Subject: Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due to a kernel NULL pointer dereference) To: Christoph Lameter References: <20150909032541.GC1998@dhcp-17-102.nay.redhat.com> <20150909071410.GD1998@dhcp-17-102.nay.redhat.com> <20150909125424.GP3644@twins.programming.kicks-ass.net> <20150914071231.GM18489@twins.programming.kicks-ass.net> <55F708D3.9090007@gmail.com> Cc: sedat.dilek@gmail.com, Peter Zijlstra , Baoquan He , Denys Vlasenko , Tejun Heo , LKML , Andrew Morton , David Rientjes , Linus Torvalds , Thomas Gleixner , Thomas Graf , Ingo Molnar , the arch/x86 maintainers From: Austin S Hemmelgarn Message-ID: <55F71408.4070702@gmail.com> Date: Mon, 14 Sep 2015 14:38:00 -0400 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-512; boundary="------------ms060604040401070905020302" X-Antivirus: avast! (VPS 150914-0, 2015-09-14), Outbound message X-Antivirus-Status: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a cryptographically signed message in MIME format. --------------ms060604040401070905020302 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: quoted-printable On 2015-09-14 14:27, Christoph Lameter wrote: > On Mon, 14 Sep 2015, Austin S Hemmelgarn wrote: > >> I can comment at least a little about the -Os aspect (although not I'm= no >> expert on this in particular). In general, for _most_ use cases, a >> kernel >> compiled with CONFIG_CC_OPTIMIZE_FOR_SIZE will run slower than one >> compiled >> without it. On rare occasion though, it may actually run faster, the >> only >> cases I've seen where this happens are specialized uses that are very >> memory >> pressure dependent and run almost entirely in userspace with almost no= >> syscalls (for example math related stuff operating on _very, very big_= >> (as in, >> >1 trillion elements) multidimensional matrices, with complex memory >> constraints), and even then it's usually a miniscule improvement in >> performance (generally less than 1%, which can of course be significan= t >> depending on how long it takes before the improvement). > > Cache footprint depends on size which has a significant impact on > performance. In our experience the kernel (and any other code) is > generally faster if optimized for size. > Ah, yes, there is that too (like I tried to say, and messed up my=20 grammar in doing so, I'm no expert), although on processors that=20 actually have a reasonable amount of cache, this is not usually=20 something most people would notice without a benchmark except on a very=20 slow processor (HPC workloads and gamers notwithstanding of course). --------------ms060604040401070905020302 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 Brgwgga0MIIEnKADAgECAgMQblUwDQYJKoZIhvcNAQENBQAweTEQMA4GA1UEChMHUm9vdCBD QTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNp Z25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcwHhcN MTUwMzI1MTkzNDM4WhcNMTUwOTIxMTkzNDM4WjBjMRgwFgYDVQQDEw9DQWNlcnQgV29UIFVz ZXIxIzAhBgkqhkiG9w0BCQEWFGFoZmVycm9pbjdAZ21haWwuY29tMSIwIAYJKoZIhvcNAQkB FhNhaGVtbWVsZ0BvaGlvZ3QuY29tMIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEA nQ/81tq0QBQi5w316VsVNfjg6kVVIMx760TuwA1MUaNQgQ3NyUl+UyFtjhpkNwwChjgAqfGd LIMTHAdObcwGfzO5uI2o1a8MHVQna8FRsU3QGouysIOGQlX8jFYXMKPEdnlt0GoQcd+BtESr pivbGWUEkPs1CwM6WOrs+09bAJP3qzKIr0VxervFrzrC5Dg9Rf18r9WXHElBuWHg4GYHNJ2V Ab8iKc10h44FnqxZK8RDN8ts/xX93i9bIBmHnFfyNRfiOUtNVeynJbf6kVtdHP+CRBkXCNRZ qyQT7gbTGD24P92PS2UTmDfplSBcWcTn65o3xWfesbf02jF6PL3BCrVnDRI4RgYxG3zFBJuG qvMoEODLhHKSXPAyQhwZINigZNdw5G1NqjXqUw+lIqdQvoPijK9J3eijiakh9u2bjWOMaleI SMRR6XsdM2O5qun1dqOrCgRkM0XSNtBQ2JjY7CycIx+qifJWsRaYWZz0aQU4ZrtAI7gVhO9h pyNaAGjvm7PdjEBiXq57e4QcgpwzvNlv8pG1c/hnt0msfDWNJtl3b6elhQ2Pz4w/QnWifZ8E BrFEmjeeJa2dqjE3giPVWrsH+lOvQQONsYJOuVb8b0zao4vrWeGmW2q2e3pdv0Axzm/60cJQ haZUv8+JdX9ZzqxOm5w5eUQSclt84u+D+hsCAwEAAaOCAVkwggFVMAwGA1UdEwEB/wQCMAAw VgYJYIZIAYb4QgENBEkWR1RvIGdldCB5b3VyIG93biBjZXJ0aWZpY2F0ZSBmb3IgRlJFRSBo ZWFkIG92ZXIgdG8gaHR0cDovL3d3dy5DQWNlcnQub3JnMA4GA1UdDwEB/wQEAwIDqDBABgNV HSUEOTA3BggrBgEFBQcDBAYIKwYBBQUHAwIGCisGAQQBgjcKAwQGCisGAQQBgjcKAwMGCWCG SAGG+EIEATAyBggrBgEFBQcBAQQmMCQwIgYIKwYBBQUHMAGGFmh0dHA6Ly9vY3NwLmNhY2Vy dC5vcmcwMQYDVR0fBCowKDAmoCSgIoYgaHR0cDovL2NybC5jYWNlcnQub3JnL3Jldm9rZS5j cmwwNAYDVR0RBC0wK4EUYWhmZXJyb2luN0BnbWFpbC5jb22BE2FoZW1tZWxnQG9oaW9ndC5j b20wDQYJKoZIhvcNAQENBQADggIBABr5e8W+NiTER+Q/7wiA2LxWN3UdhT3eZJjqqSlP370P KL5iWqeTfxQ67Ai/mHbJcT2PgAJ+/D2Ji+aRR03UWnU/vtOwzyDLUMstqnfl0Zs+sz/CJe7x nBA5jlpjC2DKuMVfbPze7eySaen7XSGFHKE1QoVIIpQ2kVjC4nbbJQnUbAVX1Iz29WxeVGt9 XYigz3tDPf3tglN+q23E7YjQl4abTIoM7i98yV1H9gfY8lFfKZ6jREB9+n6ie2EwS3Kat2mG tl2wBx4MfRnoSQSKsLKQ5oTwhWf0JqlFwpLfl374p0Njcykej9/jnWG8Ks1V/AXTHqI4eyIP Mf5yMZkPv7n7LS9WWKdG4Nd38iv4T2EiAaWsmgu+r81qL5CJu9AyA0SBS4ttKf6k3e63w2Mv N9R45vpQ3QhAhfWyFxFhZN95APe3YECDG3+XIRJpRYPEtHuIsOyzI70ajF93gg/BidvqKsmV MM2ccktDMfqwZXea6zey7F8Geu9R7BqjXmG2HlNuXu7e/xnHOgXf5D3wPmnRLlBhXL1Ch97a w2KjaupjpAHfFjv5kGnZXN87UvvlwzIZiKXwa3vTDwK+rrKn/sHPkfDZPSiyt/ZBIK6lX83P 34H/CzGg+Kx57rHYOIHGumIvpDa5vfWp8O0sGgawb1C2Aae4sTUVIWmIjVuGI062MYIE0TCC BM0CAQEwgYAweTEQMA4GA1UEChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNl cnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcN AQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxBuVTANBglghkgBZQMEAgMFAKCCAiEwGAYJKoZI hvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTUwOTE0MTgzODAwWjBPBgkq hkiG9w0BCQQxQgRAn1VU485tiSTuaHBb9QKSEcRpn1Zsj2u2gjuWtQCL/cqSPC6PJ2Dyhd9o +NUEcSH1YL20StelfL6ocwunA06d8TBsBgkqhkiG9w0BCQ8xXzBdMAsGCWCGSAFlAwQBKjAL BglghkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFA MAcGBSsOAwIHMA0GCCqGSIb3DQMCAgEoMIGRBgkrBgEEAYI3EAQxgYMwgYAweTEQMA4GA1UE ChMHUm9vdCBDQTEeMBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlD QSBDZXJ0IFNpZ25pbmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2Vy dC5vcmcCAxBuVTCBkwYLKoZIhvcNAQkQAgsxgYOggYAweTEQMA4GA1UEChMHUm9vdCBDQTEe MBwGA1UECxMVaHR0cDovL3d3dy5jYWNlcnQub3JnMSIwIAYDVQQDExlDQSBDZXJ0IFNpZ25p bmcgQXV0aG9yaXR5MSEwHwYJKoZIhvcNAQkBFhJzdXBwb3J0QGNhY2VydC5vcmcCAxBuVTAN BgkqhkiG9w0BAQEFAASCAgAmDawxb0ODZKy0CmnRpVyeYz2G7ke7+WlGPG/7jzL2mJPvCf51 8kXa13Hf+6I5Q9upYllRxPUXS+cKmLpA8RJJZB45q9uN3dSTocPljCgz7rzSZtJ4nyH4pBfl k9SkvdR2RMqUTP7incA2AtJlr+dyGHq+R56QCf4LpSDtAHPOTQzD88iO+R1pl8mdWaUn4b9R yYomSxWeitDbX4NSxQJd5gljH4YYULVMneqGKUWuAqAcwoZm5zCD0SDIMAhY+jqm7q8bGYEy di4Cso1iZu35NvgV7fYAV/SE5RXaakGxFuni9fJ9RBTM96ZygVfZujwLJEA+q9tTjrSGgUW1 X/u+AFbtKIYCQbnaM9F8xcz2r34EGfiN25gAKAqrliFRCD256nAcE7dcN/d8cbI5eUQ9fGO8 YRdidwDCxoQ5Sr9r4EOTQPsAdq0VL4fdX+9z8zV/hNvSYDdA8ItuXPmzPKJBw/uYmm6P1hjY uoXLpzMaGlSN/hsAfFOEwei3F0wOxw4gyaC+bBCTjsvRsq71gTLBYwQMpt9oVqDgdpVcM500 Fcw/buDSyNzNEAA69VlgKG2Bu0OND1M2344GKeD9mKwGUemNajT6OatFl/NJQrN/Qm0Wd/RB N8dfZ1rgz4aJyEid7nMfVyRTv1/cVG8efavDEfFKdUm/rsZp8quKZZsu6wAAAAAAAA== --------------ms060604040401070905020302--