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From Masaori Koshiba <>
Subject Re: Few Questions
Date Tue, 30 Jul 2019 05:01:52 GMT
As for 3), the drop of throughput might come from
proxy.config.cache.ram_cache_cutoff. The default size is 4MB.

- Masaori

On Tue, Jul 30, 2019 at 3:48 AM Alan Carroll <> wrote:

> 1) It's a bit more subtle than that. It depends on the size of the object.
> ATS stores objects in "fragments" and if the object fits in a single
> fragment, it's all written together. Objects larger than a fragment keep
> just the headers in the first fragment and that is what get rewritten, not
> the entire object.
> 2) No. The performance hit is very high from that and it's actually quite
> difficult at the cache writing point to do this for a single object, as
> multiple smaller writes get aggregated.
> 3) I'm not one of the performance guys, but it looks like the change in
> throughput may be due to TCP kernel socket buffer size or possibly ICW
> size. If so, you'd see higher aggregate bandwidth with parallel requests,
> which is expected usage. We have ATS doing 40+G/s in productionn for large
> files, where the limit is the network bandwidth, not ATS.
> On Sun, Jul 28, 2019 at 1:40 AM vishwas k.n. <> wrote:
>> Hello,
>> I am new to ATS and had a few questions after having installed it and
>> played around with it a bit.
>> I am primarily interested in the reverse-proxy config mode of operation
>> of ATS.
>> 1. When an origin server responds with a 304 to a request from ATS, then
>> ATS goes on to write the entire content and not just the headers into a new
>> location on the disk. This seems to be a "general space management
>> technique". In case of large files, wouldn't it make sense for the
>> directory to point to the earlier location on the disk and just update the
>> response headers ?. That way a whole chunk of write could be avoided.
>> 2. Is there a configuration to enable the AIO sync/write to the disk
>> happen immediately after the response is received from the origin server ?
>> 3. There are a few threads on the list discussing performance, however I
>> havent been able to zero in on any which discuss performance in detail.
>> We are trying to derive ATS performance benchmark using wrk as a client.
>> The initial tests suggest the below results:
>> *Iteration * *Connections/Threads (wrk)* *File Size* *Duration Of Test*
>> *ATS*
>> 1 1/1 2MB 5min 8.83 Gbps
>> 2 1/1 3MB 5min 8.27 Gbps
>> 3 1/1 4MB 5min 3.81 Gbps
>> 4 1/1 10MB 5min 3.80 Gbps
>> 5 1/1 1MB 5min 8.58 Gbps
>> The ATS configuration is used more or less the defaults available once
>> the ATS is installed.
>> The ATS version being used is 7.1.4
>> Is there a cheatsheet which indicates the tunable parameters to get
>> better performance with ATS ?
>> NOTE: I am using file cache.
>> thanks,
>> -vishwas.

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