| Zesstra | 7ea4a03 | 2019-11-26 20:11:40 +0100 | [diff] [blame^] | 1 | SYNOPSIS |
| 2 | void low_memory(int what, int limitvalue, int memory, int reservestate) |
| 3 | |
| 4 | DESCRIPTION |
| 5 | This efun is called when there is a (potential) low-memory situation. |
| 6 | Two different limits for the amount of allocated memory can be |
| 7 | configured: a soft limit and a hard limit. If the soft limit is |
| 8 | exceeded, the driver calls low_memory() but does nothing else. |
| 9 | If the hard limit is exceeded, the driver calls low_memory() as well, |
| 10 | but initiates a garbage collection directly after the call. The efun |
| 11 | is called as well directly before a user-initiated garbage collection |
| 12 | is started. |
| 13 | |
| 14 | <what> denotes the type of limit which was exceeded: |
| 15 | - NO_MALLOC_LIMIT_EXCEEDED (0) |
| 16 | No limit was exceeded, but a garbage collection was requested by a |
| 17 | call to garbage_collection() and it will begin right after |
| 18 | low_memory() returns. |
| 19 | - SOFT_MALLOC_LIMIT_EXCEEDED (1) |
| 20 | The soft limit was exceeded. |
| 21 | - HARD_MALLOC_LIMIT_EXCEEDED (2) |
| 22 | The hard limit was exceeded. A garbage collection will begin right |
| 23 | after low_memory() returns. |
| 24 | |
| 25 | <limit> specifies the numerical value of the limit which was exceeded. |
| 26 | It is 0 in case of NO_MALLOC_LIMIT_EXCEEDED. |
| 27 | |
| 28 | <memory> specifies the amount of allocated memory right now. |
| 29 | |
| 30 | <reservestate> specifies the current state of the memory reserves of |
| 31 | the driver. The states of the 3 different reserves are OR'ed together. |
| 32 | - USER_RESERVE_AVAILABLE (1) |
| 33 | The user reserve is available. |
| 34 | - MASTER_RESERVE_AVAILABLE (2) |
| 35 | The master reserve is available. |
| 36 | - SYSTEM_RESERVE_AVAILABLE (4) |
| 37 | The system reserve is available. |
| 38 | |
| 39 | This efun might be used to inform users about the garbage collection |
| 40 | and the expected long lag. |
| 41 | |
| 42 | Another possibility is to initiate a garbage collection deliberately |
| 43 | at a suitable time (e.g. during the following night) after the soft |
| 44 | limit was hit. |
| 45 | |
| 46 | REMARKS |
| 47 | If in a low_memory condition when the memory reserves have been used |
| 48 | already and they could not be re-allocated after a garbage collection |
| 49 | slow_shut_down() is called instead of calling this function again. |
| 50 | |
| 51 | HISTORY |
| 52 | Introduced in 3.3.719 |
| 53 | |
| 54 | SEE ALSO |
| 55 | debug_info(E), garbage_collection(E), slow_shut_down(M), memory(C) |
| 56 | malloc(D) |