Re: [squid-users] Re: What are recommended settings for optimal sharing of cache between SMP workers?

Needs a better hash as pointed out by the TODO :)
I will send out a patch.

Is the key guaranteed to be a null terminated string? I intend to use
std::tr1::hash

<code>
sfileno
Ipc::StoreMap::anchorIndexByKey(const cache_key *const key) const
{
    const uint64_t *const k = reinterpret_cast<const uint64_t *>(key);
    // TODO: use a better hash function
    return (k[0] + k[1]) % shared->limit;
}
</code>

On Tue, Feb 18, 2014 at 3:11 PM, Rajiv Desai <rajiv_at_maginatics.com> wrote:
> I dug deeper into the original issue I reported where some objects
> were not gettings cache HITs on subsequent reads.
>
> It seems like there is a bug where an object overwrites previously
> written object:
> For a similar "multiple downloads on same data via squid" test, I
> directed both store and cache logs to the same file store.log for
> debugging.
>
> https://s3-us-west-1.amazonaws.com/mag-1363987602-cmbogo/3f6f2db9-9750047
> is a GET request that I always get a MISS for.
> Seems like the cached object is overwritten by a subsequent GET for :
> https://s3-us-west-1.amazonaws.com/mag-1363987602-cmbogo/67f1ae81-9773953
>
> Debugging steps:
>
> 1. I extracted the store log entry for it with:
>
> <logs>
> ~$ sudo grep "GET
> https://s3-us-west-1.amazonaws.com/mag-1363987602-cmbogo/3f6f2db9-9750047"
> /mnt/squid-cache/store.log | grep SWAPOUT
> 1392764050.480 SWAPOUT 00 002DA320 A1B99D1CCFD79B73C57554BBDFDB2D89
> 200 1392764051 1392616446 1400540051 application/octet-stream
> 40384/40384 GET
> https://s3-us-west-1.amazonaws.com/mag-1363987602-cmbogo/3f6f2db9-9750047
> </logs>
>
> 2. Now I looked at all store log and cache log activity for filenum
> 002DA320 where this object was stored according to the log above
> Seems like a different object was mapped to the same filenum and
> overwrote the previous object!
>
> <logs>
> $ sudo grep 002DA320 /mnt/squid-cache/store.log
> 2014/02/18 14:54:10.311 kid6| rock/RockSwapDir.cc(628) createStoreIO:
> dir 0 created new filen 002DA320 starting at 49002594304
> 2014/02/18 14:54:10.480 kid6| store_swapout.cc(338)
> storeSwapOutFileClosed: storeSwapOutFileClosed: SwapOut complete:
> 'https://s3-us-west-1.amazonaws.com/mag-1363987602-cmbogo/3f6f2db9-9750047'
> to 0, 002DA320
> 1392764050.480 SWAPOUT 00 002DA320 A1B99D1CCFD79B73C57554BBDFDB2D89
> 200 1392764051 1392616446 1400540051 application/octet-stream
> 40384/40384 GET
> https://s3-us-west-1.amazonaws.com/mag-1363987602-cmbogo/3f6f2db9-9750047
> 2014/02/18 14:54:10.480 kid6| store_dir.cc(341) storeDirSwapLog:
> storeDirSwapLog: SWAP_LOG_ADD A1B99D1CCFD79B73C57554BBDFDB2D89 0
> 002DA320
> 2014/02/18 14:54:48.494 kid7| rock/RockSwapDir.cc(628) createStoreIO:
> dir 0 created new filen 002DA320 starting at 49002594304
> 2014/02/18 14:54:48.613 kid7| store_swapout.cc(338)
> storeSwapOutFileClosed: storeSwapOutFileClosed: SwapOut complete:
> 'https://s3-us-west-1.amazonaws.com/mag-1363987602-cmbogo/67f1ae81-9773953'
> to 0, 002DA320
> 1392764088.613 SWAPOUT 00 002DA320 26ED76867BB265254E7E39EE5C01BA9E
> 200 1392764089 1392616475 1400540089 application/octet-stream
> 25040/25040 GET
> https://s3-us-west-1.amazonaws.com/mag-1363987602-cmbogo/67f1ae81-9773953
> 2014/02/18 14:54:48.613 kid7| store_dir.cc(341) storeDirSwapLog:
> storeDirSwapLog: SWAP_LOG_ADD 26ED76867BB265254E7E39EE5C01BA9E 0
> 002DA320
> </logs>
>
> Looks like a collision bug?
>
> On Tue, Feb 18, 2014 at 6:15 AM, Dr.x <ahmed.zaeem_at_netstream.ps> wrote:
>> Amos Jeffries-2 wrote
>>> On 19/02/2014 12:12 a.m., Dr.x wrote:
>>>> im doubting ,
>>>> without smp with same traffic and same users i can save 40Mbps
>>>>
>>>> but in smp with combination of aufs with rock (32KB max obj size)
>>>> i can only save 20Mbps
>>>>
>>>>
>>>> im wondering does large rock will heal me ?
>>>>
>>>
>>> How many Squid processes are you currently needing to service those
>>> users traffic?
>>>
>>> If the number is >1 then the answer is probably yes.
>>>
>>> * Each worker should have same HIT ratio from AUFS cached objects. Then
>>> the shared Rock storage should increase HIT ratio some for workers which
>>> would not normally see those small objects.
>>>
>>>
>>>> or return to aufs and wait untill squid relase version that has bigger
>>>> object size ?
>>>>
>>>> bw saving is a big issue to me and must be done !!!
>>>>
>>>
>>> Your choice there.
>>>
>>> FYI: The upcoming Squid series with large-rock support is not planned to
>>> be packaged for another 3-6 months.
>>>
>>> HTH
>>> Amos
>>
>> hi amos ,
>> i have about 900 req/sec , and i think i need 4 or 5 workers at maximum
>> i have 24 cores ,
>> from the old squid that was saving 40-45M i found mean object size
>> Mean Object Size: *142.30 KB*
>>
>> i found that 142KB is close to 100KB ,
>>
>> i mean if i used large rock , will it enhace byte ratio !!!
>> do agree with me ?
>>
>> now regardsing to use aufs with rock
>>
>> now i have 5 aufs hardsisk each has conf file and aufs dir and max object
>> size
>>
>> now , wt is the best implementation of smp ?
>>
>> should i do if statements and map each worker with aufs process ?
>>
>> im not sure which is best
>>
>> sure u can give me advice to start ,
>>
>>
>> also , can i use large rock now ?
>> regards
>>
>>
>>
>>
>> -----
>> Dr.x
>> --
>> View this message in context: http://squid-web-proxy-cache.1019090.n4.nabble.com/What-are-recommended-settings-for-optimal-sharing-of-cache-between-SMP-workers-tp4664909p4664921.html
>> Sent from the Squid - Users mailing list archive at Nabble.com.
Received on Wed Feb 19 2014 - 00:33:16 MST