= Сообщение: 8925 из 10753 ===================================== RU.UNIX.BSD = От : Slawa Olhovchenkov 2:5030/500 06 May 19 13:13:38 Кому : Eugene Grosbein 06 May 19 13:13:38 Тема : parallel mounting for ZFS filesystem FGHI : area://RU.UNIX.BSD?msgid=2:5030/500+5cd00957 На : area://RU.UNIX.BSD?msgid=grosbein.net+4409546e = Кодировка сообщения определена как: FIDO =================================== ============================================================================== Hello Eugene!
06 May 19, Eugene Grosbein writes to Slawa Olhovchenkov:
AK>>>> обещал там кто-то или оно случайно работало правильно - совершенно AK>>>> никому неинтересно. Сломали ненужным улучшизмом - чините. EG>>> Сначала нужно найти в спецификации, а было ли что ломать изначально. SO>> в спецификации есть ARC алгоритм. его сломали. и что дальше? EG> А дай ссылочку на спецификацию.
/* * DVA-based Adjustable Replacement Cache * * While much of the theory of operation used here is * based on the self-tuning, low overhead replacement cache * presented by Megiddo and Modha at FAST 2003, there are some * significant differences: * * 1. The Megiddo and Modha model assumes any page is evictable. * Pages in its cache cannot be "locked" into memory. This makes * the eviction algorithm simple: evict the last page in the list. * This also make the performance characteristics easy to reason * about. Our cache is not so simple. At any given moment, some * subset of the blocks in the cache are un-evictable because we * have handed out a reference to them. Blocks are only evictable * when there are no external references active. This makes * eviction far more problematic: we choose to evict the evictable * blocks that are the "lowest" in the list. * * There are times when it is not possible to evict the requested * space. In these circumstances we are unable to adjust the cache * size. To prevent the cache growing unbounded at these times we * implement a "cache throttle" that slows the flow of new data * into the cache until we can make space available. * * 2. The Megiddo and Modha model assumes a fixed cache size. * Pages are evicted when the cache is full and there is a cache * miss. Our model has a variable sized cache. It grows with * high use, but also tries to react to memory pressure from the * operating system: decreasing its size when system memory is * tight. * * 3. The Megiddo and Modha model assumes a fixed page size. All * elements of the cache are therefore exactly the same size. So * when adjusting the cache size following a cache miss, its simply * a matter of choosing a single page to evict. In our model, we * have variable sized cache blocks (rangeing from 512 bytes to * 128K bytes). We therefore choose a set of blocks to evict to make * space for a cache miss that approximates as closely as possible * the space used by the new block. * * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache" * by N. Megiddo & D. Modha, FAST 2003 */
... Специалист подобен флюсу: полнота его одностороння. --- GoldED+/BSD 1.1.5-b20110223-b20110223 * Origin: (2:5030/500)
