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c067a55c79
Converting size to usize is what jemalloc has been done by ceiling size to the closest size class. However, this causes lots of memory wastes with HPA enabled. This commit changes how usize is calculated so that the gap between two contiguous usize is no larger than a page. Specifically, this commit includes the following changes: 1. Adding a build-time config option (--enable-limit-usize-gap) and a runtime one (limit_usize_gap) to guard the changes. When build-time config is enabled, some minor CPU overhead is expected because usize will be stored and accessed apart from index. When runtime option is also enabled (it can only be enabled with the build-time config enabled). a new usize calculation approach wil be employed. This new calculation will ceil size to the closest multiple of PAGE for all sizes larger than USIZE_GROW_SLOW_THRESHOLD instead of using the size classes. Note when the build-time config is enabled, the runtime option is default on. 2. Prepare tcache for size to grow by PAGE over GROUP*PAGE. To prepare for the upcoming changes where size class grows by PAGE when larger than NGROUP * PAGE, disable the tcache when it is larger than 2 * NGROUP * PAGE. The threshold for tcache is set higher to prevent perf regression as much as possible while usizes between NGROUP * PAGE and 2 * NGROUP * PAGE happen to grow by PAGE. 3. Prepare pac and hpa psset for size to grow by PAGE over GROUP*PAGE For PAC, to avoid having too many bins, arena bins still have the same layout. This means some extra search is needed for a page-level request that is not aligned with the orginal size class: it should also search the heap before the current index since the previous heap might also be able to have some allocations satisfying it. The same changes apply to HPA's psset. This search relies on the enumeration of the heap because not all allocs in the previous heap are guaranteed to satisfy the request. To balance the memory and CPU overhead, we currently enumerate at most a fixed number of nodes before concluding none can satisfy the request during an enumeration. 4. Add bytes counter to arena large stats. To prepare for the upcoming usize changes, stats collected by multiplying alive allocations and the bin size is no longer accurate. Thus, add separate counters to record the bytes malloced and dalloced. 5. Change structs use when freeing to avoid using index2size for large sizes. - Change the definition of emap_alloc_ctx_t - Change the read of both from edata_t. - Change the assignment and usage of emap_alloc_ctx_t. - Change other callsites of index2size. Note for the changes in the data structure, i.e., emap_alloc_ctx_t, will be used when the build-time config (--enable-limit-usize-gap) is enabled but they will store the same value as index2size(szind) if the runtime option (opt_limit_usize_gap) is not enabled. 6. Adapt hpa to the usize changes. Change the settings in sec to limit is usage for sizes larger than USIZE_GROW_SLOW_THRESHOLD and modify corresponding tests. 7. Modify usize calculation and corresponding tests. Change the sz_s2u_compute. Note sz_index2size is not always safe now while sz_size2index still works as expected. |
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| doc | ||
| doc_internal | ||
| include | ||
| m4 | ||
| msvc | ||
| scripts | ||
| src | ||
| test | ||
| .appveyor.yml | ||
| .autom4te.cfg | ||
| .cirrus.yml | ||
| .clang-format | ||
| .gitattributes | ||
| .gitignore | ||
| .travis.yml | ||
| autogen.sh | ||
| ChangeLog | ||
| config.stamp.in | ||
| configure.ac | ||
| COPYING | ||
| INSTALL.md | ||
| jemalloc.pc.in | ||
| Makefile.in | ||
| README | ||
| run_tests.sh | ||
| TUNING.md | ||
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: https://jemalloc.net/