In some cases processMultibulkBuffer uses sdsMakeRoomFor to
expand the querybuf, but later in some cases it uses that query
buffer as is for an argv element (see "Optimization"), which means
that the sds in argv may have a lot of wasted space, and then in case
modules keep that argv RedisString inside their data structure, this
space waste will remain for long (until restarted from rdb).
In MEMORY USAGE command, we count the key argv[2] into usage,
but the argument in command may contains free spaces because of
sdsMakeRoomFor. But the key in db never contains free spaces
because we use sdsdup when dbAdd, so using the real key to
count the usage is more accurate.
RESTORE now supports:
1. Setting LRU/LFU
2. Absolute-time TTL
Other related changes:
1. RDB loading will not override LRU bits when RDB file
does not contain the LRU opcode.
2. RDB loading will not set LRU/LFU bits if the server's
maxmemory-policy does not match.
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
The main change introduced by this commit is pretending that help
arrays are more text than code, thus indenting them at level 0. This
improves readability, and is an old practice when defining arrays of
C strings describing text.
Additionally a few useless return statements are removed, and the HELP
subcommand capitalized when printed to the user.
It's a bit of black magic without actually tracking it inside rax.c,
however Redis usage of the radix tree for the stream data structure is
quite consistent, so a few magic constants apparently are producing
results that make sense.
This adds a new `addReplyHelp` helper that's used by commands
when returning a help text. The following commands have been
touched: DEBUG, OBJECT, COMMAND, PUBSUB, SCRIPT and SLOWLOG.
WIP
Fix entry command table entry for OBJECT for HELP option.
After #4472 the command may have just 2 arguments.
Improve OBJECT HELP descriptions.
See #4472.
WIP 2
WIP 3
Firstly, use access time to replace the decreas time of LFU.
For function LFUDecrAndReturn,
it should only try to get decremented counter,
not update LFU fields, we will update it in an explicit way.
And we will times halve the counter according to the times of
elapsed time than server.lfu_decay_time.
Everytime a key is accessed, we should update the LFU
including update access time, and increment the counter after
call function LFUDecrAndReturn.
If a key is overwritten, the LFU should be also updated.
Then we can use `OBJECT freq` command to get a key's frequence,
and LFUDecrAndReturn should be called in `OBJECT freq` command
in case of the key has not been accessed for a long time,
because we update the access time only when the key is read or
overwritten.
