Why redis need zmalloc?

[wenhao wen]

Hi, everyone.
I am reading the source code of redis, and wondering why redis replace
malloc with zmalloc.
What's the usage of the header of the memory?
Thank you so much

[Salvatore Sanfilippo]

Hello, there is no other way to have a real-time and precise metrics
of the allocated memory otherwise.

Thanks to zmalloc Redis can implement maxmemory easily, you can do
something like:

while (used_memory() > configured_max_memory) {
evict_smoe_object();
}

There are no other ways to do this, there is even a lack of
platform-specific non portable ways.

Cheers,
Salvatore

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Salvatore 'antirez' Sanfilippo
open source developer - VMware

http://invece.org
"We are what we repeatedly do. Excellence, therefore, is not an act,
but a habit." -- Aristotele

[redis.f...@gmail.com]

Hello Salvatore,

I was wondering what exactly did mean by "real-time and precise".

Isn't /proc/self/status real-time and precise (assuming I don't care about portability)?

If that is really the case, could you please explain why? How can I verify it?

Best regards,