Since the dynamic allocations in raxIterator are only used for deep walks, memory
leak due to missing call to raxStop can only happen for rax with key names longer
than 32 bytes.
Out of all the missing calls, the only ones that may lead to a leak are the rax
for consumer groups and consumers, and these were only in AOFRW and rdbSave, which
normally only happen in fork or at shutdown.
There's a rare case which leads to stagnation in the defragger, causing
it to keep scanning the keyspace and do nothing (not moving any
allocation), this happens when all the allocator slabs of a certain bin
have the same % utilization, but the slab from which new allocations are
made have a lower utilization.
this commit fixes it by removing the current slab from the overall
average utilization of the bin, and also eliminate any precision loss in
the utilization calculation and move the decision about the defrag to
reside inside jemalloc.
and also add a test that consistently reproduce this issue.
When active defrag kicks in and finds a big list, it will create a bookmark to
a node so that it is able to resume iteration from that node later.
The quicklist manages that bookmark, and updates it in case that node is deleted.
This will increase memory usage only on lists of over 1000 (see
active-defrag-max-scan-fields) quicklist nodes (1000 ziplists, not 1000 items)
by 16 bytes.
In 32 bit build, this change reduces the maximum effective config of
list-compress-depth and list-max-ziplist-size (from 32767 to 8191)
Reduce default minimum effort, so that when fragmentation is just detected,
the impact on the latency will be minor.
Reduce the default maximum effort, mainly to prevent a case were a sudden
massive deletions, won't trigger an aggressive defrag that will cause latency.
When activedefrag is disabled mid-run, reset the 'running' info field, and
clear the scan cursor, so that when it'll be re-enabled, a new fresh scan will
start.
Clearing the 'running' variable is important since lowering the defragger
tunables mid-scan won't help, the defragger only considers new threshold when
a new scan starts, and during a scan it can only become more aggressive,
(when more severe fragmentation is detected), it'll never go less aggressive.
So by temporarily disabling activedefrag, one can lower th the tunables.
Removing the experimantal warning.
cluster.c - stack buffer memory alignment
The pointer 'buf' is cast to a more strictly aligned pointer type
evict.c - lazyfree_lazy_eviction, lazyfree_lazy_eviction always called
defrag.c - bug in dead code
server.c - casting was missing parenthesis
rax.c - indentation / newline suggested an 'else if' was intended
* create module API for forking child processes.
* refactor duplicate code around creating and tracking forks by AOF and RDB.
* child processes listen to SIGUSR1 and dies exitFromChild in order to
eliminate a valgrind warning of unhandled signal.
* note that BGSAVE error reply has changed.
valgrind error is:
Process terminating with default action of signal 10 (SIGUSR1)
on slower machines, the active defrag test tended to fail.
although the fragmentation ratio was below the treshold, the defragger was
still in the middle of a scan cycle.
this commit changes:
- the defragger uses the current fragmentation state, rather than the cache one
that is updated by server cron every 100ms. this actually fixes a bug of
starting one excess scan cycle
- the test lets the defragger use more CPU cycles, in hope that the defrag
will be faster, but also give it more time before we give up.
other fixes / improvements:
- LUA script memory isn't taken from zmalloc (taken from libc malloc)
so it can cause high fragmentation ratio to be displayed (which is false)
- there was a problem with "fragmentation" info being calculated from
RSS and used_memory sampled at different times (now sampling them together)
other details:
- adding a few more allocator info fields to INFO and MEMORY commands
- improve defrag test to measure defrag latency of big keys
- increasing the accuracy of the defrag test (by looking at real grag info)
this way we can use an even lower threshold and still avoid false positives
- keep the old (total) "fragmentation" field unchanged, but add new ones for spcific things
- add these the MEMORY DOCTOR command
- deduct LUA memory from the rss in case of non jemalloc allocator (one for which we don't "allocator active/used")
- reduce sampling rate of the rss and allocator info
- big keys are not defragged in one go from within the dict scan
instead they are scanned in parts after the main dict hash bucket is done.
- add latency monitor sample for defrag
- change default active-defrag-cycle-min to induce lower latency
- make active defrag start a new scan right away if needed, so it's easier
(for the test suite) to detect when it's done
- make active defrag quick the current cycle after each db / big key
- defrag some non key long term global allocations
- some refactoring for smaller functions and more reusable code
- during dict rehashing, one scan iteration of the dict, can end up scanning
one bucket in the smaller dict and many many buckets in the larger dict.
so waiting for 16 scan iterations before checking the time, may be much too long.
Don't go over 80 cols. Start with captial letter, capital letter afer
point, end comment with a point and so forth. No actual code behavior
touched at all.
