site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 I'm wondering if there is a way to "recover" an equivalent memory descriptor from a memory descriptors virtual address. Here's more detail. We use a user client interface to pass a large buffer to the kernel to read some data. This buffer is allocated in user space and passed into the user client to become the structureOutputDescriptor of the IOExternalMethodArguments. Due to our cross platform interface, this buffer is converted to a memory address and length using. The memory address is determined using IOMemoryDescriotor::map() and getVirtualAddress() on the resulting IOMemoryMap. Later this self same address must be used to read data from the disk. This is accomplished using IOMemoryDescriptor::withAddress() using the virtual address determined previously. Would this second memory descriptor be fundamentally equivalent to the first? Using the same addresses etc? Is there a way of making that happen? My fear is that this process is contributing to virtual memory fragmentation or at least not making the best use of available virtual memory. It appears that in some cases this process fails when creating the second IOMemoryDescriptor using IOMemoryDescriptor::withAddress(). The proper solution would, of course, be to be able to get the original memory descriptor to the IO routine. Unfortunately that may prove to be rather difficult given our cross platform engine. Thank you for any suggestions and insight to the workings of IOMemoryDescriptors, ...Duane -----BEGIN PGP SIGNATURE----- Version: PGP Desktop 9.10.0 (Build 500) Charset: US-ASCII wsBVAwUBSvhkjUrg9acQ4r2CAQjsKQf/dAoyMQISsrNBv6ylyia7rBnmJ5jmccGq AtQW2eEvblZM3w9Hdl7BF/ZTjVI/FZ1khFcZKq3Eb2EWEniKI67G8jgcuW6PktJc IhBOxNQRXJMvtPsHShTXYwGA386/n1fSX3VrKh4tk2AAEt9K1GcqcWHBaZ7aFBo3 yEDMuhmGDvjTZJLamISPPa4Zu6tzIflVIUNlQYj+sFvGHuV6yVMd/U/e2Oajq2gx Ek47UBJ9qKH4UagTmpBe962QTyvGhmzaA1NX0EXPhrAT4+Mm3TaPWakWVHxU33HV ebcVDV3in63WgHbfMfvOfuri9RTo/Cww85KTD1ifzs5+9Gk5hvoy0g== =C4pP -----END PGP SIGNATURE----- _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.a... This email sent to site_archiver@lists.apple.com