Transparent hardware-assisted memory decompression

Patent metadata

Field	Value
Publication number	US-2016239209-A1
Application number	US-201615043023-A
Country	US
Kind code	A1
Filing date	Feb 12, 2016
Priority date	Feb 13, 2015
Publication date	Aug 18, 2016
Grant date	—

Abstract

Provided are methods and systems for memory decompression using a hardware decompressor that minimizes or eliminates the involvement of software. Custom decompression hardware is added to the memory subsystem, where the decompression hardware handles read accesses caused by, for example, cache misses or requests from devices to compressed memory blocks, by reading a compressed block, decompressing it into an internal buffer, and returning the requested portion of the block. The custom hardware is designed to determine if the block is compressed, and determine the parameters of compression, by checking unused high bits of the physical address of the access. This allows compression to be implemented without additional metadata, because the necessary metadata can be stored in unused bits in the existing page table structures.

First claim

1 . A hardware decompressor, the decompressor comprising:
a hardware device disposed between a processing unit and a physical computer memory, wherein the hardware device is configured to:
receive a memory access read request, the received request causing a cache miss or page fault;
determine whether data requested by the memory access read request is in a compressed memory block;
responsive to a determination that the data requested by the memory access read request is not in a compressed memory block, forward the memory access read request to the physical computer memory;
responsive to a determination that the data requested by the memory access read request is in a compressed memory block, determine whether the data from the compressed memory block has been previously decompressed and stored in a dedicated storage medium local to the hardware device;
responsive to a determination that the data from the compressed memory block is stored in the storage medium, return the data from the storage medium in response to the memory access read request; and
responsive to a determination that the data from the compressed memory block is not stored in the storage medium,
allocate storage space in the storage medium;
read the data from the compressed memory block;
decompress the read data from the compressed memory block into the storage medium; and
return the decompressed data from the storage medium in response to the memory access read request.

2 . The hardware decompressor of claim 1 , wherein the hardware device is configured to:
read the data from the compressed memory block until the data requested by the memory access read request is located; and decompress the read data from the compressed memory block into the storage medium only to the point where the requested data is fully retrieved.

3 . The hardware decompressor of claim 1 , wherein the hardware device is configured to:
determine whether the data requested by the memory access read request is in the compressed memory block by checking unused bits of page table structures that store information about virtual memory pages.

4 . The hardware decompressor of claim 1 , wherein the hardware device is configured to:
selectively alternate between a full memory decompression mode and a partial memory decompression mode.

5 . The hardware decompressor of claim 4 , wherein the hardware device is configured to:
alternate between the full memory decompression mode and the partial memory decompression mode based on one or more performance parameters of a device or program associated with the received memory access read request.

6 . The hardware decompressor of claim 4 , wherein the hardware device is configured to:
alternate between the full memory decompression mode and the partial memory decompression mode based on a signal received from a device or program associated with the received memory access read request.

7 . A method for memory decompression, the method comprising:
receiving a memory access read request, the received request causing a cache miss or page fault to occur; determining whether data requested by the memory access read request is in a compressed memory block; in response to determining that the data requested by the memory access read request is not in a compressed memory block, sending the memory access read request to a physical computer memory; in response to determining that the data requested by the memory access read request is in a compressed memory block, determining whether the data from the compressed memory block has previously been decompressed by a hardware decompression device and stored in a dedicated storage medium local to the hardware decompression device; in response to determining that the data from the compressed memory block is stored in the dedicated storage medium local to the hardware decompression device, returning the data from the storage medium in response to the received memory access read request; and in response to determining that the data from the compressed memory block is not stored in the dedicated storage medium local to the hardware decompression device,
allocating storage space in the storage medium local to the hardware decompression device;
reading the data from the compressed memory block;
decompressing the read data from the compressed memory block into the storage medium local to the hardware decompression device; and
returning the decompressed data from the storage medium in response to the memory access read request.

8 . The method of claim 7 , wherein the hardware decompression device is disposed between a processing unit and the physical computer memory.

9 . The method of claim 7 , further comprising:
reading the data from the compressed memory block until the data requested by the memory access read request is located; and decompressing the read data from the compressed memory block into the storage medium local to the hardware decompression device only to the point where the requested data is fully retrieved.

10 . The method of claim 7 , further comprising:
determining whether the data requested by the memory access read request is in the compressed memory block by checking unused bits of page table structures that store information about virtual memory pages.

11 . The method of claim 7 , further comprising:
selectively alternating between a full memory decompression mode and a partial memory decompression mode.

12 . The method of claim 11 , wherein the alternation between the full memory decompression mode and the partial memory decompression mode is based on one or more performance parameters of a device or program associated with the received memory access read request.

13 . The method of claim 11 , wherein the alternation between the full memory decompression mode and the partial memory decompression mode is based on a signal received from a device or program associated with the received memory access read request.

14 . A system for memory decompression, the system comprising:
system memory; at least one processor coupled to the system memory; and a non-transitory computer-readable medium associated with the at least one processor, the non-transitory medium having instructions stored thereon that, when executed by the at least one processor, causes the at least one processor to:
receive a memory access read request, the received request causing a cache miss or page fault to occur;
determine whether data requested by the memory access read request is in a compressed memory block;
in response to determining that the data requested by the memory access read request is not in a compressed memory block, send the memory access read request to the system memory;
in response to determining that the data requested by the memory access read request is in a compressed memory block, determine whether the data from the compressed memory block has previously been decompressed and stored in a dedicated storage medium local to the at least one processor;
in response to determining that the data from the compressed memory block is stored in the storage medium, return the data from the storage medium in response to the received memory access read request; and
in response to determining that the data from the compressed memory block is not stored in the storage medium,
allocate storage space in the storage medium;
read the data from the compressed memory block;
decompress the read data from the compressed memory block into the storage medium; and
return the decompressed data from the storage medium in response to the memory access read request

Assignees

• Google Inc

Inventors

• Malyugin Vyacheslav Vladimirovich
• Semenzato Luigi
• Chng Choon Ping
• Rao Santhosh
• Shiu Shinye

Classifications

• G06F3/0673

  Single storage device · CPC title

• G06F3/0604

  Improving or facilitating administration, e.g. storage management · CPC title

• G06F3/064 Primary

  Management of blocks · CPC title

• G06F3/0631

  by allocating resources to storage systems · CPC title

• G06F3/0656

  Data buffering arrangements · CPC title