In general, you can predict fairly closely what a given object will require. There’s some overhead that is relatively fixed, plus the instance fields in the object, plus a modest amount of padding. But then object size is rounded up to at least (on most JVMs) a 16-byte boundary, and some JVMs round up some object sizes to larger boundaries (to allow the use of standard sized pre-allocated object frames). But all this is relatively fixed for a given JVM.<\/p>\n
What varies, of course, is the overhead required for garbage collection. A naive garbage collector requires 100% overhead (at least one free byte for every allocated byte), though certain varieties of “generational” collectors can improve on this to a degree. But how much space is required for GC is highly dependent on the workload (on most JVMs).<\/p>\n
The other problem is that when you’re running at a relatively low level of allocation (where you’re only using maybe 10% of max available heap) then garbage will accumulate. It isn’t actively referenced, but the bits of garbage are interspersed with your active objects, so it takes up working set. As a result, your working set tends to be roughly equal to your current overall garbage-collected heap size (plus other system overhead).<\/p>\n
You can, of course, “throttle” the heap size so that you run at a higher % utilization, but that increases the frequency of garbage collection (and the overall cost of GC to a lesser degree).<\/p>\n","protected":false},"excerpt":{"rendered":"
In general, you can predict fairly closely what a given object will require. There’s some overhead that is relatively fixed, plus the instance fields in the object, plus a modest amount of padding. But then object size is rounded up to at least (on most JVMs) a 16-byte boundary, and some JVMs round up some […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-5058","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts\/5058","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/comments?post=5058"}],"version-history":[{"count":0,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts\/5058\/revisions"}],"wp:attachment":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/media?parent=5058"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/categories?post=5058"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/tags?post=5058"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}