Re: Increasing row retrieving speed via net8
- From: GG <grzegorzof@xxxxxxxxxx>
- To: Timur Akhmadeev <Akhmadeev@xxxxxxxxxxxxxx>
- Date: Wed, 18 Apr 2012 18:35:48 +0200
W dniu 2012-04-18 11:30, Timur Akhmadeev pisze:
> Hi
>
> Why do you think futex calls are your problem? JVM is multi-threaded by
> default and threads do use different system calls during their life. Doesn't
> mean your particular Net issue has anything to do with futex calls, which
> are, as far as I know, ~idle work.
>
Hi,
if I remember correctly pmdtm is not java aps but it uses threads, I saw
nine when using 1 data fetch stream .
Getting back to futex , as You've said its not about futex 'as is' but
rather number of calls to futex .
I've got sample strace taken in ~ 10 sec interval for both bad and good
performing fetch ( select * from table )
cat 1t_bad.txt 1t_8M_buffer.out
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
57.35 1.738975 161 10819 2145 futex
41.35 1.253799 32149 39 poll
1.21 0.036717 3 11869 read
0.08 0.002491 1 2163 write
0.00 0.000000 0 50 fcntl
0.00 0.000000 0 19 clock_gettime
------ ----------- ----------- --------- --------- ----------------
100.00 3.031982 24959 2145 total
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
61.90 0.754143 3969 190 24 futex
37.27 0.454022 14188 32 poll
0.82 0.010002 1 11062 read
0.01 0.000070 2 31 write
0.00 0.000000 0 50 fcntl
0.00 0.000000 0 14 clock_gettime
------ ----------- ----------- --------- --------- ----------------
100.00 1.218237 11379 24 total
So for small buffer 120kB I think (was able to fetch 30k rows per sec)
it was like
10819 futex calls and 2145 errors related
and with 8MB buffer (was able to fetch 105k rows per sec) it was like:
190 futex calls 24 errors
So instead of 'futexing' threads was doing read from socket descriptor
to 8M application buffer :).
BTW that buffer size is directly related to fetch size (r=_FETCH_SIZE_
in 10046 fetch call) set by client connection .
Hope that helps .
Regards
GregG
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