Real-time open file cache hashing table restructuring in a server computer

• US 5,835,756 A
• Filed: 11/27/1996
• Issued: 11/10/1998
• Est. Priority Date: 06/04/1993
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Digital Equipment Corporation (HP Inc.)
• Inventors: Caccavale, Frank Samuel
• Primary Examiner(s): Heckler, Thomas M.
• Application Number:
  US08/758,682
• Time in Patent Office: 713 Days
• Field of Search: 395/601, 395/616, 395/621, 395/421.06, 395/421.11, 395/445, 395/460, 395/486
• US Class Current: 1/1
• CPC Class Codes: G06F 11/32 with visual or acoustical indication of the functioning of the machine
• CPC Class Codes: G06F 11/323 Visualisation of programs or trace data
• CPC Class Codes: G06F 11/328 Computer systems status display G06F11/327 takes precedence
• CPC Class Codes: G06F 11/3419 by assessing time
• CPC Class Codes: G06F 11/3433 for load management allocation of a server based on load conditions G06F9/505; load rebalancing G06F9/5083; redistributing the load in a network by a load balancer H04L67/1029
• CPC Class Codes: G06F 11/3452 Performance evaluation by statistical analysis
• CPC Class Codes: G06F 11/3495 for systems
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache
• CPC Class Codes: G06F 2201/805 Real-time
• CPC Class Codes: G06F 2201/885 Monitoring specific for caches
• CPC Class Codes: G06F 2212/601 Reconfiguration of cache memory
• CPC Class Codes: H04L 43/00 Arrangements for monitoring or testing data switching networks
• CPC Class Codes: H04L 43/12 Network monitoring probes
• CPC Class Codes: H04L 43/16 Threshold monitoring
• CPC Class Codes: H04L 67/01 Protocols
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: Y10S 707/99931 Database or file accessing

Abstract

In a method and system for dynamically improving the performance of a server in a network, a tuning system monitors a workload of the server in real time, monitors a set of internal performance characteristics of the server in real time, and monitors a set of adjustable server parameters of the server in real time. The workload of the server may include the frequency and type of service requests received by the server from clients in the network. The internal server performance characteristics may include, for example, a data cache hit ratio of a data cache in the server. The set of server parameters may include, for example, the overall data cache size or the data cache geometry of the server. The tuning system periodically alters one or more of the set of adjustable server parameters as a function of the workload and internal performance characteristics of the server. Since the tuning system is continuously monitoring workload and performance characteristics of the server and altering the server parameters accordingly, the effectiveness of a given change in the server parameters is reflected in the next set of monitored workload and performance values.

Claims

1. A method of operating a storage system, comprising the steps of:

periodically determining (1) a number n of file header structure elements stored in a hashing table in a memory in the storage system, each element containing a copy of file header information from a corresponding file stored on a mass storage device in the storage system coupled to the memory in which the hashing table is stored, and (2) a number n_s representing an average number of elements in the hashing table that are searched in response to file access requests before the element required by each request is found, n_s being a function of both n and the structure of the hashing table;

calculating a moving average value n_s-avg-t equal to the moving average of n_s, over a number of most recent periods;

recording the values of n_s-avg-t over multiple periods;

determining from the recorded values of n_s-avg-t whether n_s-avg-t is exhibiting saturation behavior;

if n_s-avg-t is exhibiting saturation behavior, then performing the following steps;

a) selecting a value of n_s-avg-t from a recent period during which n_s-avg-t was not exhibiting saturation behavior;

b) determining a new structure for the hashing table using the most recently determined value for n and the selected value of n_s-avg-t, the new structure being such that the average number of elements in such a newly-structured hashing table that would be searched in response to file access requests before the element required by each request would be found is equal to n_s-avg-t when the number of elements in such a newly-structured hashing table is n; and

c) changing the structure of the hashing table to the determined new structure; and

if n_s-avg-t is not exhibiting saturation behavior, then refraining from so changing the structure of the hashing table.

2. A method according to claim 1, wherein:

the hashing table is arranged to have a number m of slots each containing sequentially-arranged ones of the file header structure elements;

each search requires (a) the determination of which slot contains the required element, and (b) the sequential examination of each element in the slot until the required element is found;

the step of determining a new structure for the hashing table comprises the steps of a) calculating a new value for m equal to (n-1)/ 2(n_s-avg-t -1)!, and b) changing the number of slots in the hashing table to the calculated new value for m; and

the step of refraining from changing structure of the hashing table comprises the step of refraining from so changing the number of slots in the hashing table.