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Linux based cache managers will allocate vcaches on demand and deallocate batches of vcaches in the background. This feature is called dynamic vcaches. Vcaches to be deallocated are found by traversing the vcache LRU list (VLRU) from the oldest vcache to the newest. Up to a target number of vcaches are attempted to be evicted. The afs_xvcache lock protecting the VLRU may be dropped and re-acquired while attempting to evict a vcache. When this happens, it is possible the VLRU may have changed, so the traversal of the VLRU is restarted. This restarting of the VLRU transversal is limited to 100 iterations to avoid looping indefinitely. Vcaches which are busy cannot be evicted and remain in the VLRU. When a busy cache was not evicted and the afs_xvache lock was dropped, the VLRU traversal is restarted from the end of the VLRU. When the busy vcache is encountered on the retry, it will trigger additional retries until the loop limit is reached, at which point the target number of vcaches will not be deallocated. This can leave a very large number of unbusy vcaches which are never deallocated. On a busy machine, tens of millions of unused vcaches can remain in memory. When the busy vcache at the end of the VLRU is finally evicted, the log jam is broken, and the background deamon will hold the afs_xvcache lock for an excessively long time, hanging the system. Fix this by moving busy vcaches to the head of the VLRU before restarting the VLRU traversal. These busy vcaches will be skipped when retrying the VLRU traversal, allowing the cache manager to make progress deallocating vcaches down to the target level. This was already done on the mac osx platform while attempting to evict vcaches. Move the code to move busy vcaches to the head of the VLRU up the the platform agnostic caller. Thanks to Andrew Deason for the initial version of this patch. Change-Id: I7768d00604e56d8d5369ac5215f7c2ab7996c4eb Reviewed-on: https://gerrit.openafs.org/11654 Tested-by: BuildBot <buildbot@rampaginggeek.com> Reviewed-by: Andrew Deason <adeason@dson.org> Reviewed-by: Benjamin Kaduk <kaduk@mit.edu> |
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| build-tools | ||
| doc | ||
| src | ||
| tests | ||
| .gitignore | ||
| .splintrc | ||
| acinclude.m4 | ||
| CODING | ||
| configure-libafs.ac | ||
| configure.ac | ||
| CONTRIBUTING | ||
| INSTALL | ||
| libafsdep | ||
| LICENSE | ||
| Makefile-libafs.in | ||
| Makefile.in | ||
| NEWS | ||
| NTMakefile | ||
| README | ||
| README-WINDOWS | ||
| regen.sh | ||
AFS is a distributed file system that enables users to share and access all of the files stored in a network of computers as easily as they access the files stored on their local machines. The file system is called distributed for this exact reason: files can reside on many different machines, but are available to users on every machine. OpenAFS 1.0 was originally released by IBM under the terms of the IBM Public License 1.0 (IPL10). For details on IPL10 see the LICENSE file in this directory. The current OpenAFS distribution is licensed under a combination of the IPL10 and many other licenses as granted by the relevant copyright holders. The LICENSE file in this directory contains more details, thought it is not a comprehensive statement. See INSTALL for information about building and installing OpenAFS on various platforms. See CODING for developer information and guidelines. See NEWS for recent changes to OpenAFS.