Re: Troubleshoot clone issue to NFS.

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On Thu, May 21, 2015 at 10:53 PM,  <steve.norman@xxxxxxxxxxxxxxxxxx> wrote:
> On Thu, May 21, 2015a at 9:31 PM, Duy Nguyen [mailto:pclouds@xxxxxxxxx], did scribble:
>> > In case an object is not found pack directory is re-read again, which
>> > might cause some increased load on nfs.
>> > has_sha1_file() not finding the object should not happen often..
>>
>> That last statement is probably very wrong, but I have no time to test this
>> now. In index-pack, there is a has_sha1_file() for file collision test. That call
>> on a fresh clone would fail for _every_ object in the
>> (new) pack and the cost of reprepare pack files could be sky high...
>
> Confirmed with bisect that it is that commit:
>
> ~/git $ git bisect bad
> 45e8a7487339c0f0ea28244ef06851308d07387c is the first bad commit
> commit 45e8a7487339c0f0ea28244ef06851308d07387c
> Author: Jeff King <peff@xxxxxxxx>
> Date:   Fri Aug 30 15:14:13 2013 -0400
>
> I have an strace for that build but it is 153 megabytes so I probably shouldn't attach, but the call summary is below:
>
> % time     seconds  usecs/call     calls    errors syscall
> ------ ----------- ----------- --------- --------- ----------------
>  93.71   39.670084         103    386835      2171 futex
>   3.16    1.338572           7    190550       181 open
>   1.56    0.658786          18     37450         3 read
>   0.62    0.262740           2    141390           pread
>   0.41    0.171526           5     37313         9 write
>   0.18    0.076166           0    188859    188835 access
>   0.11    0.047941           0    374712           getdents
>   0.11    0.045174          11      4067      3910 lstat
>   0.06    0.023630           0    190425           close
>   0.04    0.017995           6      2975         1 fstat
>   0.02    0.007668        1917         4           wait4
>   0.01    0.004150           1      5065           madvise
>   0.01    0.003548           0     16090         8 recvfrom
>   0.00    0.001872           0      8048           select
>   0.00    0.001870          11       173         1 mkdir
>   0.00    0.000872           0      8055           poll
>   0.00    0.000262          22        12        12 readlink
>   0.00    0.000185           0      1217      1146 stat
>   0.00    0.000158           0       457           mprotect
>   0.00    0.000074           0       298           mmap
>   0.00    0.000069           1       109         8 rt_sigreturn
>   0.00    0.000047           0       159           brk
>   0.00    0.000021           1        17           getcwd
>   0.00    0.000000           0        42         3 lseek
>   0.00    0.000000           0        92           munmap
>   0.00    0.000000           0        35           rt_sigaction
>   0.00    0.000000           0         9           rt_sigprocmask
>   0.00    0.000000           0         8         3 ioctl
>   0.00    0.000000           0        11           pipe
>   0.00    0.000000           0         3           dup
>   0.00    0.000000           0         8           dup2
>   0.00    0.000000           0         6           setitimer
>   0.00    0.000000           0        11         1 socket
>   0.00    0.000000           0         8         7 connect
>   0.00    0.000000           0         8           sendto
>   0.00    0.000000           0         2           recvmsg
>   0.00    0.000000           0         1           bind
>   0.00    0.000000           0         1           getsockname
>   0.00    0.000000           0         3         1 getpeername
>   0.00    0.000000           0         2           setsockopt
>   0.00    0.000000           0         2           getsockopt
>   0.00    0.000000           0         8           clone
>   0.00    0.000000           0         5           execve
>   0.00    0.000000           0         3           uname
>   0.00    0.000000           0       100           fcntl
>   0.00    0.000000           0         2           fsync
>   0.00    0.000000           0        13           chdir
>   0.00    0.000000           0        14           rename
>   0.00    0.000000           0         2           link
>   0.00    0.000000           0         5           unlink
>   0.00    0.000000           0         2           symlink
>   0.00    0.000000           0         9           chmod
>   0.00    0.000000           0         6           getrlimit
>   0.00    0.000000           0         2           sysinfo
>   0.00    0.000000           0         8           getuid
>   0.00    0.000000           0         1           statfs
>   0.00    0.000000           0         5           arch_prctl
>   0.00    0.000000           0         1           gettid
>   0.00    0.000000           0         5           set_tid_address
>   0.00    0.000000           0        13           set_robust_list
> ------ ----------- ----------- --------- --------- ----------------
> 100.00   42.333410               1594736    196300 total
>
> Is there anything else I can provide or test?

In builtin/index-pack.c, replace the line "collision_test_needed =
has_sha1_file(sha1);" with "collision_test_needed = 0;". Security is
compromised but for this test it should be ok. Then clone again. I
hope the new number gets down close to v1.8.4.1.
-- 
Duy
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