0f6c420f83
Before this change, purge/hugify decisions had several sharp edges that could lead to pathological behavior if tuning parameters weren't carefully chosen. It's the first of a series; this introduces basic "make every hugepage with dirty pages purgeable" functionality, and the next commit expands that functionality to have a smarter policy for picking hugepages to purge. Previously, the dehugify logic would *never* dehugify a hugepage unless it was dirtier than the dehugification threshold. This can lead to situations in which these pages (which themselves could never be purged) would push us above the maximum allowed dirty pages in the shard. This forces immediate purging of any pages deallocated in non-hugified hugepages, which in turn places nonobvious practical limitations on the relationships between various config settings. Instead, we make our preference not to dehugify to purge a soft one rather than a hard one. We'll avoid purging them, but only so long as we can do so by purging non-hugified pages. If we need to purge them to satisfy our dirty page limits, or to hugify other, more worthy candidates, we'll still do so.
jemalloc is a general purpose malloc(3) implementation that emphasizes fragmentation avoidance and scalable concurrency support. jemalloc first came into use as the FreeBSD libc allocator in 2005, and since then it has found its way into numerous applications that rely on its predictable behavior. In 2010 jemalloc development efforts broadened to include developer support features such as heap profiling and extensive monitoring/tuning hooks. Modern jemalloc releases continue to be integrated back into FreeBSD, and therefore versatility remains critical. Ongoing development efforts trend toward making jemalloc among the best allocators for a broad range of demanding applications, and eliminating/mitigating weaknesses that have practical repercussions for real world applications. The COPYING file contains copyright and licensing information. The INSTALL file contains information on how to configure, build, and install jemalloc. The ChangeLog file contains a brief summary of changes for each release. URL: http://jemalloc.net/