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Posted to issues@trafficserver.apache.org by GitBox <gi...@apache.org> on 2022/09/28 10:33:03 UTC
[GitHub] [trafficserver] frostnotfall opened a new issue, #9111: Confused about memory allocation
frostnotfall opened a new issue, #9111:
URL: https://github.com/apache/trafficserver/issues/9111
I want to know about memory allocation.
I think there are 2 parts of memory allocation, both are disk storage relevant.
1. RAM Cache .
2. Cache directory is used as a memory resident structure
# RAM Cache
There are 2 statements, but contradictory.
1. 10MB to 1GB. https://docs.trafficserver.apache.org/en/latest/admin-guide/performance/index.en.html?highlight=ssd#memory-allocation
2. 1MB to 1GB. https://docs.trafficserver.apache.org/en/latest/admin-guide/storage/index.en.html#changing-the-size-of-the-ram-cache
Q: what is real?
# Cache directory is used as a memory resident structure
Q: How do i calculate it？
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[GitHub] [trafficserver] cmcfarlen closed issue #9111: Confused about memory allocation
Posted by GitBox <gi...@apache.org>.
cmcfarlen closed issue #9111: Confused about memory allocation
URL: https://github.com/apache/trafficserver/issues/9111
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[GitHub] [trafficserver] frostnotfall commented on issue #9111: Confused about memory allocation
Posted by GitBox <gi...@apache.org>.
frostnotfall commented on issue #9111:
URL: https://github.com/apache/trafficserver/issues/9111#issuecomment-1261724456
> Reading the code I see that, unless the size is specified, the ram cache for each cache volume is set to 10x the directory length of the volume (in bytes). Running an experiment, this worked out to about 1.2% of the total configured cache size. Based on this, the 10MB per 1GB is closer to correct. Since this is based on the cache size and not available RAM, I recommend you specify the ram cache size in your config rather than rely on this heuristic. I think this was just meant to be a gentle default.
>
> I'm sorry but I do not understand the second part of your question.
# Cache directory is used as a memory resident structure
In my opinion, Disk cache directory has indexed in memory. As HDD space grows, so does memory usage.
So, for example, how many memory the indexes are used when for 1TB hard disk.
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[GitHub] [trafficserver] cmcfarlen commented on issue #9111: Confused about memory allocation
Posted by GitBox <gi...@apache.org>.
cmcfarlen commented on issue #9111:
URL: https://github.com/apache/trafficserver/issues/9111#issuecomment-1273464687
If you run traffic_server with the `-Tcache_init` argument, it will print some allocation info about space used for directory vs volume size:
```
(init)> (cache_init) Vol /opt/ats/var/trafficserver/cache.db 16384:2883584: allocating 29474816 directory bytes for a 23622320128 byte volume (0.124775%)
```
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[GitHub] [trafficserver] frostnotfall commented on issue #9111: Confused about memory allocation
Posted by GitBox <gi...@apache.org>.
frostnotfall commented on issue #9111:
URL: https://github.com/apache/trafficserver/issues/9111#issuecomment-1276991367
Post my test.
My settings：
12 HDD * 3TB = 36TB, close RamCache, the mem usage is 50.16GB.
(In addition, my machine has 12 HDD, every is 8TB，but I can‘t use all of them， because I just have 64GB memory)
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[GitHub] [trafficserver] cmcfarlen commented on issue #9111: Confused about memory allocation
Posted by GitBox <gi...@apache.org>.
cmcfarlen commented on issue #9111:
URL: https://github.com/apache/trafficserver/issues/9111#issuecomment-1261444816
Reading the code I see that, unless the size is specified, the ram cache for each cache volume is set to 10x the directory length of the volume (in bytes). Running an experiment, this worked out to about 1.2% of the total configured cache size. Based on this, the 10MB per 1GB is closer to correct. Since this is based on the cache size and not available RAM, I recommend you specify the ram cache size in your config rather than rely on this heuristic. I think this was just meant to be a gentle default.
I'm sorry but I do not understand the second part of your question.
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