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diff --git a/manual/tunables.texi b/manual/tunables.texi index 9331b03702..b16d591b90 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -193,6 +193,38 @@ systems the limit is twice the number of cores online and on 64-bit systems, it is 8 times the number of cores online. @end deftp +@deftp Tunable glibc.malloc.tcache_max +The maximum size of a request (in bytes) which may be met via the +per-thread cache. The default (and maximum) value is 1032 bytes on +64-bit systems and 516 bytes on 32-bit systems. +@end deftp + +@deftp Tunable glibc.malloc.tcache_count +The maximum number of chunks of each size to cache. The default is 7. +There is no upper limit, other than available system memory. If set +to zero, the per-thread cache is effectively disabled. + +The approximate maximum overhead of the per-thread cache is thus equal +to the number of bins times the chunk count in each bin times the size +of each chunk. With defaults, the approximate maximum overhead of the +per-thread cache is approximately 236 KB on 64-bit systems and 118 KB +on 32-bit systems. +@end deftp + +@deftp Tunable glibc.malloc.tcache_unsorted_limit +When the user requests memory and the request cannot be met via the +per-thread cache, the arenas are used to meet the request. At this +time, additional chunks will be moved from existing arena lists to +pre-fill the corresponding cache. While copies from the fastbins, +smallbins, and regular bins are bounded and predictable due to the bin +sizes, copies from the unsorted bin are not bounded, and incur +additional time penalties as they need to be sorted as they're +scanned. To make scanning the unsorted list more predictable and +bounded, the user may set this tunable to limit the number of chunks +that are scanned from the unsorted list while searching for chunks to +pre-fill the per-thread cache with. The default, or when set to zero, +is no limit. + @node Hardware Capability Tunables @section Hardware Capability Tunables @cindex hardware capability tunables |