From aa81e4d5f4b4d942b9340fd2d401e7795fa9fd1e Mon Sep 17 00:00:00 2001 From: antirez Date: Fri, 31 Dec 2010 18:23:31 +0100 Subject: [PATCH] minor changes to doc and comments --- redis.conf | 96 ++++++++++++++------------------------------------- src/db.c | 2 +- src/dscache.c | 2 ++ 3 files changed, 28 insertions(+), 72 deletions(-) diff --git a/redis.conf b/redis.conf index 3efd1e59..3425a59c 100644 --- a/redis.conf +++ b/redis.conf @@ -291,77 +291,31 @@ appendfsync everysec # "no" that is the safest pick from the point of view of durability. no-appendfsync-on-rewrite no -################################ VIRTUAL MEMORY ############################### - -# Virtual Memory allows Redis to work with datasets bigger than the actual -# amount of RAM needed to hold the whole dataset in memory. -# In order to do so very used keys are taken in memory while the other keys -# are swapped into a swap file, similarly to what operating systems do -# with memory pages. -# -# To enable VM just set 'vm-enabled' to yes, and set the following three -# VM parameters accordingly to your needs. - -vm-enabled no -# vm-enabled yes - -# This is the path of the Redis swap file. As you can guess, swap files -# can't be shared by different Redis instances, so make sure to use a swap -# file for every redis process you are running. Redis will complain if the -# swap file is already in use. -# -# The best kind of storage for the Redis swap file (that's accessed at random) -# is a Solid State Disk (SSD). -# -# *** WARNING *** if you are using a shared hosting the default of putting -# the swap file under /tmp is not secure. Create a dir with access granted -# only to Redis user and configure Redis to create the swap file there. -vm-swap-file /tmp/redis.swap - -# vm-max-memory configures the VM to use at max the specified amount of -# RAM. Everything that deos not fit will be swapped on disk *if* possible, that -# is, if there is still enough contiguous space in the swap file. -# -# With vm-max-memory 0 the system will swap everything it can. Not a good -# default, just specify the max amount of RAM you can in bytes, but it's -# better to leave some margin. For instance specify an amount of RAM -# that's more or less between 60 and 80% of your free RAM. -vm-max-memory 0 - -# Redis swap files is split into pages. An object can be saved using multiple -# contiguous pages, but pages can't be shared between different objects. -# So if your page is too big, small objects swapped out on disk will waste -# a lot of space. If you page is too small, there is less space in the swap -# file (assuming you configured the same number of total swap file pages). -# -# If you use a lot of small objects, use a page size of 64 or 32 bytes. -# If you use a lot of big objects, use a bigger page size. -# If unsure, use the default :) -vm-page-size 32 - -# Number of total memory pages in the swap file. -# Given that the page table (a bitmap of free/used pages) is taken in memory, -# every 8 pages on disk will consume 1 byte of RAM. -# -# The total swap size is vm-page-size * vm-pages -# -# With the default of 32-bytes memory pages and 134217728 pages Redis will -# use a 4 GB swap file, that will use 16 MB of RAM for the page table. -# -# It's better to use the smallest acceptable value for your application, -# but the default is large in order to work in most conditions. -vm-pages 134217728 - -# Max number of VM I/O threads running at the same time. -# This threads are used to read/write data from/to swap file, since they -# also encode and decode objects from disk to memory or the reverse, a bigger -# number of threads can help with big objects even if they can't help with -# I/O itself as the physical device may not be able to couple with many -# reads/writes operations at the same time. -# -# The special value of 0 turn off threaded I/O and enables the blocking -# Virtual Memory implementation. -vm-max-threads 4 +#################################### DISK STORE ############################### + +# When disk store is active Redis works as an on-disk database, where memory +# is only used as a object cache. +# +# This mode is good for datasets that are bigger than memory, and in general +# when you want to trade speed for: +# +# - less memory used +# - immediate server restart +# - per key durability, without need for backgrond savig +# +# On the other hand, with disk store enabled MULTI/EXEC are no longer +# transactional from the point of view of the persistence on disk, that is, +# Redis transactions will still guarantee that commands are either processed +# all or nothing, but there is no guarantee that all the keys are flushed +# on disk in an atomic way. +# +# Of course with disk store enabled Redis is not as fast as it is when +# working with just the memory back end. + +diskstore-enabled no +diskstore-path redis.ds +cache-max-memory 0 +cache-flush-delay 0 ############################### ADVANCED CONFIG ############################### diff --git a/src/db.c b/src/db.c index 1a30034e..1f185e29 100644 --- a/src/db.c +++ b/src/db.c @@ -19,7 +19,7 @@ robj *lookupKey(redisDb *db, robj *key) { if (server.ds_enabled && val->storage == REDIS_DS_SAVING) { /* FIXME: change this code to just wait for our object to - * get out of the IO Job. */ + * get out of the IO Job. As it is now it is correct but slow. */ waitEmptyIOJobsQueue(); processAllPendingIOJobs(); redisAssert(val->storage != REDIS_DS_SAVING); diff --git a/src/dscache.c b/src/dscache.c index a56fa118..5551420a 100644 --- a/src/dscache.c +++ b/src/dscache.c @@ -109,6 +109,8 @@ * Also, make sure that key preloading is ONLY done for keys that are * not marked as cacheKeyDoesNotExist(), otherwise, again, we can load * data from disk that should instead be deleted. + * + * - dsSet() use rename(2) in order to avoid corruptions. */ /* Virtual Memory is composed mainly of two subsystems: -- 2.47.2