A method for operating a memory (28) that includes a plurality of analog memory cells (32) includes storing data in the memory by writing first storage values to the cells. Second storage values are read from the cells, and a Cumulative Distribution Function (CDF) of the second storage values is estimated. The estimated CDF is processed so as to compute one or more thresholds. A memory access operation is performed on the cells using the one or more thresholds.

Adaptive Estimation of Memory Cell Read Thresholds

A method for operating a memory (28) includes storing data, which is encoded with an Error Correction Code (ECC), in analog memory cells (32) of the memory by writing respective analog input values selected from a set of nominal values to the analog memory cells. The stored data is read by performing multiple read operations that compare analog output values of the analog memory cells to different, respective read thresholds so as to produce multiple comparison results for each of the analog memory cells. At least two of the read thresholds are positioned between a pair of the nominal values that are adjacent to one another in the set of the nominal values. Soft metrics are computed responsively to the multiple comparison results. The ECC is decoded using the soft metrics, so as to extract the data stored in the analog memory cells.

Reading memory cells using multiple thresholds

A method for operating a memory (28) includes storing data in a group of analog memory cells (32) of the memory as respective first voltage levels. After storing the data, second voltage levels are read from the respective analog memory cells. The second voltage levels are affected by cross-coupling interference causing the second voltage levels to differ from the respective first voltage levels. Cross-coupling coefficients, which quantify the cross-coupling interference among the analog memory cells, are estimated by processing the second voltage levels. The data stored in the group of analog memory cells is reconstructed from the read second voltage levels using the estimated cross-coupling coefficients.

Distortion estimation and cancellation in memory devices

A method for storing data in a memory (28) that includes analog memory cells (32) includes identifying one or more defective memory cells in a group of the analog memory cells. An Error Correction Code (ECC) is selected responsively to a characteristic of the identified defective memory cells. The data is encoded using the selected ECC and the encoded data is stored in the group of the analog memory cells. In an alternative method, an identification of one or more defective memory cells among the analog memory cells is generated. Analog values are read from the analog memory cells in which the encoded data were stored, including at least one of the defective memory cells. The analog values are processed using an ECC decoding process responsively to the identification of the at least one of the defective memory cells, so as to reconstruct the data.

Automatic defect management in memory devices

A method for operating a memory device (24) includes encoding data using an Error Correction Code (ECC) and storing the encoded data as first analog values in respective analog memory cells (32) of the memory device. After storing the encoded data, second analog values are read from the respective memory cells of the memory device in which the encoded data were stored. At least some of the second analog values differ from the respective first analog values. A distortion that is present in the second analog values is estimated. Error correction metrics are computed with respect to the second analog values responsively to the estimated distortion. The second analog values are processed using the error correction metrics in an ECC decoding process, so as to reconstruct the data.

Combined distortion estimation and error correction coding for memory devices

In accordance with one or more aspects, compressed storage management in a system includes determining which of multiple data units stored in an uncompressed portion of the storage resource are to be compressed and stored in a compressed portion of the storage resource The management can further include returning one or more regions of the compressed portion for use in the uncompressed portion in response to storage resource pressure in the system, as well as compacting regions in the compressed portion to fill empty gaps in the compressed portion

Compressed storage management

Embodiments of the invention provide techniques for ensuring that the contents of a non-volatile memory device may be relied upon as accurately reflecting data stored on disk storage across a power transition such as a reboot. For example, some embodiments of the invention provide techniques for determining whether the cache contents and/or or disk contents are modified during a power transition, causing cache contents to no longer accurately reflect data stored in disk storage. Further, some embodiments provide techniques for managing cache metadata during normal ("steady state") operations and across power transitions, ensuring that cache metadata may be efficiently accessed and reliably saved and restored across power transitions.

Managing cache data and metadata

Resume of a computing device from hibernation may be performed in multiple phases. Each phase may partially restore a state of the computing device to an operational state and may establish an environment in which another phase of the resume is performed. The hibernation information may be partitioned to store separately data to be used at each resume phase. The information may be stored in a compressed form. In a first phase, a boot-level resume loader may restore a portion of the operating system based on a portion of the hibernation information. The restored portion may be used in a second phase to retrieve hibernation information from another portion through the operating system (OS). Multiple processors supported by the OS may read and decompress the hibernation information that is then moved back to operational memory. The operating system may support asynchronous disk input/output or other functions that accelerate the resume process.

Multi-phase resume from hibernate

A memory scanning system may scan memory objects to determine usage frequency by scanning each memory object using a mapping of the processes stored in memory. The scanning may be performed multiple times to generate a usage history for each page or unit of memory. In some cases, scanning may be performed at different frequencies to determine multiple classifications of usage. The mapping may create a detailed topology of memory usage, including multiple classifications of access frequency, as well as several other classifications. Based on the topology, the objects in memory may be copied to another storage medium or optimized for performance or power consumption.

Memory usage scanning

Fast computer startup is provided by, upon receipt of a shutdown command, recording state information representing a target state. In this target state, the computing device may have closed all user sessions, such that no user state information is included in the target state. However, the operating system may still be executing. In response to a command to startup the computer, this target state may be quickly reestablished from the recorded target state information. Portions of a startup sequence may be performed to complete the startup process, including establishing user state. To protect user expectations despite changes in response to a shutdown command, creation and use of the file holding the recorded state information may be conditional on dynamically determined events. Also, user and programmatic interfaces may provide options to override creation or use of the recorded state information.

Yevgeniy M. Bak

Papers

Compressed storage management

Managing cache data and metadata

Multi-phase resume from hibernate

Memory usage scanning

Fast computer startup