Efficient reclamation of pre-allocated direct memory access (DMA) memory

Patent metadata

Field	Value
Publication number	US-9582223-B2
Application number	US-201414252146-A
Country	US
Kind code	B2
Filing date	Apr 14, 2014
Priority date	Apr 14, 2014
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

For efficient reclamation of pre-allocated direct memory access (DMA) memory in a computing environment, hot-add random access memory (RAM) is emulated for a general purpose use by reclamation of pre-allocated DMA memory reserved at boot time for responding to an emergency by notifying a non-kernel use device user that the non-kernel use device has a smaller window, stopping and remapping to the smaller window, and notifying a kernel that new memory has been added, wherein the new memory is a region left after the remap.

First claim

What is claimed is:

1. A method for efficient reclamation of pre-allocated direct memory access (DMA) memory using a processor device in a computing environment, the method comprising:
emulating a hot-add RAM for a general purpose use by reclamation of pre-allocated DMA memory reserved at boot time by notifying a non-kernel use device user that the non-kernel use device has a smaller window, stopping and remapping to the smaller window, and notifying a kernel that new memory has been added, wherein the new memory is a region left after the remap;
stopping the application requiring the non-kernel use device;
stopping operations of the non-kernel use device by a device driver; and
unmapping a buffer from a kernel virtual mapping system.

2. The method of claim 1 , further including splitting the hot-add RAM into at least two continuous parts.

3. The method of claim 2 , further including remapping at least one of the two continuous parts of the hot-add RAM for use by DMA memory of the non-kernel use device, wherein the new memory is at least one of the two continuous parts.

4. The method of claim 3 , further including signaling the kernel of the addition of the hot-add RAM.

5. The method of claim 4 , further including performing at least one of:
scanning the at least one of the two continuous parts of the hot-add RAM by the kernel,
perceiving that the least one of the two continuous parts of the hot-add RAM is newly added, and
adding the least one of the two continuous parts of the hot-add RAM to a pool of general purpose memory.

6. The method of claim 5 , further including configuring the non-kernel use device with the buffer of the least one of the two continuous parts of the hot-add RAM.

7. A system for efficient reclamation of pre-allocated direct memory access (DMA) memory in a computing environment, the system comprising:
at least one processor device operable in the computing environment, wherein the at least one processor device:
emulates a hot-add random access memory (RAM) for a general purpose use by reclamation of pre-allocated DMA memory reserved at boot time by notifying a non-kernel use device user that the non-kernel use device has a smaller window, stopping and remapping to the smaller window, and notifying a kernel that new memory has been added, wherein the new memory is a region left after the remap,

stops the application requiring the non-kernel use device,
stops operations of the non-kernel use device by a device driver, and
unmaps a buffer from a kernel virtual mapping system.

8. The system of claim 7 , wherein the at least one processor device splits the hot-add RAM into at least two continuous parts.

9. The system of claim 8 , wherein the at least one processor device remaps at least one of the two continuous parts of the hot-add RAM for use by DMA memory of the non-kernel use device, wherein the new memory is at least one of the two continuous parts.

10. The system of claim 9 , wherein the at least one processor device signals the kernel of the addition of the hot-add RAM.

11. The system of claim 10 , wherein the at least one processor device performs at least one of:
scanning the at least one of the two continuous parts of the hot-add RAM by the kernel,
perceiving that the least one of the two continuous parts of the hot-add RAM is newly added, and
adding the least one of the two continuous parts of the hot-add RAM to a pool of general purpose memory.

12. The system of claim 11 , wherein the at least one processor device configuring the non-kernel use device with the buffer of the least one of the two continuous parts of the hot-add RAM.

13. A computer program product for efficient reclamation of pre-allocated direct memory access (DMA) memory using a processor device, the computer program product comprising a non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising:
a first executable portion that emulates a hot-add random access memory (RAM) for a general purpose use by reclamation of pre-allocated DMA memory reserved at boot time by notifying a non-kernel use device user that the non-kernel use device has a smaller window, stopping and remapping to the smaller window, and notifying a kernel that new memory has been added, wherein the new memory is a region left after the remap; and
a second executable portion that stops the application requiring the non-kernel use device,
stops operations of the non-kernel use device by a device driver, and
unmaps a buffer from a kernel virtual mapping system.

14. The computer program product of claim 13 , further includes a third executable portion that performs at least one of:
splitting the hot-add RAM into at least two continuous parts, and
remapping at least one of the two continuous parts of the hot-add RAM for use by DMA memory of the non-kernel use device, wherein the new memory is at least one of the two continuous parts.

15. The computer program product of claim 14 , further includes a fourth executable portion that signals the kernel of the addition of the hot-add RAM.

16. The computer program product of claim 15 , further includes a fifth executable portion that performs at least one of:
scanning the at least one of the two continuous parts of the hot-add RAM by the kernel,
perceiving that the least one of the two continuous parts of the hot-add RAM is newly added, and
adding the least one of the two continuous parts of the hot-add RAM to a pool of general purpose memory.

17. The computer program product of claim 16 , further includes a sixth executable portion that configures the non-kernel use device with the buffer of the least one of the two continuous parts of the hot-add RAM.

Assignees

• IBM

Inventors

• Akirav Shay H
• Bar Oren
• Barsky Roman
• Maoz Itay

Classifications

• G06F3/0683 Primary

  Plurality of storage devices · CPC title

• G06F12/1081 Primary

  for peripheral access to main memory, e.g. direct memory access [DMA] · CPC title

• G06F9/4401

  Bootstrapping (security arrangements therefor G06F21/57) · CPC title