query on pmem on redis

[muneendra kumar]

Hi ,

Iam running redis on emulated pmem device using the below link.

https://github.com/pmem/pmem-redis

I am using the default redis.conf available in the above git hub and just enabled the below options

appendonly =yes

and run my server using the below command

[root@pmem4]# ./redis-server redis.conf  --nvm-maxcapacity 1 --nvm-dir /mnt/pmem4

and running the benchmark test to study the performance.

redis-benchmark -h 127.0.0.1 -p 6379 -t set,lpush -n 100000 -q  -d 32 -r 100000 

Query:

In the /mnt/pmem4 directory i observed two files.

redis-port-6379-1GB-AEP, and appendonly.aof files

And when i hexdump these two file both has some valid data

Can someone explain what are these two files.

When i looked into the code all the memory needed for setCommand is coming from

mmap memory of redis-port-6379-1GB-AEP file .IS my understanding correct?

Regards,

Muneendra.

[Peifeng Si]

Hi Muneendra,

If you enable the option "appendonly", redis stores a copy of key-value pairs in a disk file (e.g. appendonly.aof). With it, all key-value pairs can be restored after rebooting host or restarting redis-server.

Besides, as usual, for the key-values in memory, their spaces are allocated from a memory mapping file (e.g., redis-port-6379-1GB-AEP) on NVM.

Thanks,

Peifeng

在 2019年2月12日星期二 UTC+8下午8:43:53，muneendra kumar写道：

[muneendra kumar]

Hi Peifeng,

Thanks for your reply.

I have one more query on the same.

Can i store  appendonly.aof file  in PMEM mount directory i.e /mnt/pmem4 ? 

 

If i give appendfsync always in the redis.conf file i observed couple of writes happening into the appendonly.aof file,

For all these write operations we need a buffer to write(server.aof_buf) ,is this buffer also coming from spaces allocated from a memory mapping file  or it's a cached buffer ?

Regards,

Muneendra.

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[Peifeng Si]

Muneendra,

Please see my reply inline with the prefix ">>PSI".

Thanks,

Peifeng

在 2019年2月13日星期三 UTC+8下午2:24:01，muneendra kumar写道：

Hi Peifeng,

Thanks for your reply.

I have one more query on the same.

Can i store  appendonly.aof file  in PMEM mount directory i.e /mnt/pmem4 ? 

>>PSI: yes, you can. or you can store it on another high speed disk drive.

 

If i give appendfsync always in the redis.conf file i observed couple of writes happening into the appendonly.aof file,

For all these write operations we need a buffer to write(server.aof_buf) ,is this buffer also coming from spaces allocated from a memory mapping file  or it's a cached buffer ? 

 >> PSI: No, aof_buf is allocated from DRAM.