Browse Prior Art Database

Method for enhancing aging precision with minimal storage overhead in memory salvaging applications

IP.com Disclosure Number: IPCOM000012551D
Publication Date: 2003-May-14
Document File: 4 page(s) / 96K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for enhancing aging precision with minimal storage overhead in memory salvaging applications. Benefits include improved performance and improved data quality.

This text was extracted from a Microsoft Word document.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 35% of the total text.

Method for enhancing aging precision with minimal storage overhead in memory salvaging applications

             

Disclosed is a method for enhancing aging precision with minimal storage overhead in memory salvaging applications. Benefits include improved performance and improved data quality.

Background

      Systems that use complex memory management techniques have a high risk for memory leakage if some design factors are not considered. Memory leakage issues escape presilicon validation due to the low probability of its occurrence. However, in silicon, the issue is present even if the leakage is very slow. Over time, the leakage builds up and reduces the memory available for operation. In networking products, this issue is especially critical because the system cannot be reset to recover the leaked memory. In addition, the high cost of silicon revisions makes having a contingency mechanism in place for salvaging leaked memory while the system is in use almost mandatory.

              Conventionally, an aging function is the contingency mechanism. The aging function keeps a global timer for the current time. Each state of the timer lasts for a finite time duration and is called the time zone (the zone). The aging function marks the current time on each of the linked list nodes (or entries) of the managed memory, as long as the node is active. The aging function periodically compares the time marked on each of the nodes with the current time. If the time stamp on the node is sufficiently different from the current zone, the entry is old.

              Because this salvaging function is only a contingency function and not the primary mechanism, on-chip resource overhead resulting from the scheme must be minimized. The aging function is a low priority process, occurring within a range of a few minutes. As a result, conventional aging schemes have several issues. A number of bits must be allocated to store the time stamp. In a typical switch having 8k nodes in the managed memory linked list and 3 bits for storing the time stamp, about 24k bits are used for storing the time stamp.

              In the conventional aging function, entries are compared to the current time around the zone change (see Figure 1). With this approach, distinguishing between the entries that became inactive close to the zone change at points A and B becomes difficult. The check for aged entries can be delayed until the next zone change. This approach resolves the issue with the entries that became inactive near point B. However, issues remain for the entries that became inactive around point A because those entries are not salvaged for a longer time. If the check for the aged entries occurs after one zone change, the minimum and maximum aging time is:

Tmin = 0, Tmax = 1 zones

              If the check for the aged entries after two zone changes, the minimum and maximum aging time is:

Tmin = 1 zones, Tmax = 2 zones

              Consequently, more than one bit must be used to ensure that...