On 05/24/2012 06:25 PM, Maxim Dounin wrote:
>> Does it suggest nginx issues? Because the second nginx instance
>> serves the files fine.
>>
>> Or maybe some system / sysctl parameters?
>
> It suggests you are disk-bound and all nginx workers are busy
> waiting for I/O operations. Try looking here for basic
> optimization steps:
>
> http://mailman.nginx.org/pipermail/nginx/2012-May/033761.html
I've tried to follow these recommendations, but don't really see any improvement.
The systems are not disk bound (see below).
Even if I try to fetch a file which is stored in tmpfs, it is slow - 20, 30 secs, even more, like here:
[root@da1 ~]# time curl ca3/404/404.html
curl: (7) couldn't connect to host
real 1m3.204s
user 0m0.000s
sys 0m0.000s
I see it only when the number of established connections to nginx is around 700 and more (most serving large files, so the connections are long-lived).
Disk load:
root@ca2:~# iostat -k 1
(...)
avg-cpu: %user %nice %system %iowait %steal %idle
21.23 0.00 25.69 2.41 0.00 50.66
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 0.00 0.00 0.00 0 0
sdb 26.00 1240.00 0.00 1240 0
sdc 23.00 2324.00 0.00 2324 0
sdd 12.00 916.00 0.00 916 0
sde 9.00 532.00 0.00 532 0
sdf 9.00 532.00 0.00 532 0
sdg 9.00 532.00 0.00 532 0
sdh 22.00 2196.00 0.00 2196 0
sdi 32.00 1044.00 172.00 1044 172
sdj 5.00 20.00 0.00 20 0
sdk 13.00 1044.00 0.00 1044 0
sdl 17.00 1556.00 0.00 1556 0
sdm 18.00 940.00 0.00 940 0
root@ca2:~# iostat -x 1
avg-cpu: %user %nice %system %iowait %steal %idle
21.81 0.00 29.46 4.46 0.00 44.26
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
sdb 0.00 26.00 6.00 2.00 1536.00 224.00 220.00 0.00 0.00 0.00 0.00
sdc 0.00 0.00 18.00 0.00 2656.00 0.00 147.56 0.04 2.22 1.11 2.00
sdd 0.00 33.00 4.00 3.00 1024.00 288.00 187.43 0.00 0.00 0.00 0.00
sde 0.00 26.00 4.00 2.00 768.00 224.00 165.33 0.00 0.00 0.00 0.00
sdf 0.00 23.00 1.00 2.00 192.00 200.00 130.67 0.02 6.67 6.67 2.00
sdg 0.00 27.00 6.00 2.00 560.00 232.00 99.00 0.09 11.25 2.50 2.00
sdh 0.00 39.00 28.00 19.00 2392.00 464.00 60.77 0.24 5.11 0.85 4.00
sdi 0.00 0.00 8.00 0.00 1792.00 0.00 224.00 0.02 2.50 1.25 1.00
sdj 0.00 25.00 0.00 2.00 0.00 216.00 108.00 0.00 0.00 0.00 0.00
sdk 0.00 0.00 8.00 0.00 2048.00 0.00 256.00 0.03 3.75 2.50 2.00
sdl 0.00 28.00 14.00 2.00 1152.00 240.00 87.00 0.00 0.00 0.00 0.00
sdm 0.00 60.00 4.00 3.00 1024.00 504.00 218.29 0.01 1.43 1.43 1.00
--
Tomasz Chmielewski
http://www.ptraveler.com
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