On Tue, Jan 3, 2012 at 5:35 PM, ronjpark <nginx-forum@nginx.us> wrote:
> Hello everyone,
>
> Firstly, I'm sorry for posting the same question here and there (How to
> forum).
> It is urgent issue to me.
>
> Could you give me a tip for which directives and values I have to set
> for the optimization?
>
> I installed nginx on virtual machine as reverse proxy server.
> It checks the authentication and bypasses the client request to the
> backend servers.
> The most transactions are to upload/download files, from 1M to 1G...
>
> The CPU usage hits 100% when the 1M file download request reaches around
> 25 TPS..
> around 20 TPS for upload request..
>
> I set client_body_buffer_size, proxy_buffer_size, proxy_buffers and so
> on..
> But not so good yet.. :(
>
> client_body_buffer_size is set to 2M and it helps to increase TPS for
> uploading, but not enough.
> proxy_buffer_size = 1M and proxy_buffers = 4 1M help to increase TPS for
> downloading little bit, but not so much..
> Other directives are set by its default.
>
> The below is the result of profiling with google_proftools_module.
> As you can see, the most time is spent on readv() and writev().
>
> Please give me any advice or your experience.
> Thank you for your time.
>
> Total: 22244 samples
> 11928 53.6% 53.6% 11930 53.6% readv
> 8212 36.9% 90.5% 8212 36.9% writev
> 907 4.1% 94.6% 907 4.1% recv
> 359 1.6% 96.2% 359 1.6% __connect_nocancel
> 248 1.1% 97.3% 248 1.1% __close_nocancel
> 35 0.2% 97.5% 46 0.2% _IO_str_pbackfail
> 34 0.2% 97.7% 34 0.2% __write_nocancel
> 31 0.1% 97.8% 31 0.1% socket
> 28 0.1% 97.9% 28 0.1% memset
> and
> Total: 64475 samples
> 34117 52.9% 52.9% 34117 52.9% writev
> 14173 22.0% 74.9% 14181 22.0% readv
> 11981 18.6% 93.5% 11981 18.6% recv
> 1046 1.6% 95.1% 1049 1.6% __connect_nocancel
> 878 1.4% 96.5% 878 1.4% __close_nocancel
> 343 0.5% 97.0% 343 0.5% epoll_wait
> 160 0.2% 97.2% 160 0.2% __write_nocancel
> 89 0.1% 97.4% 89 0.1% __xstat64
> 81 0.1% 97.5% 115 0.2% _IO_str_pbackfail
>
>
> Here is the information of my VM:
> ronjpark@PSEProxy:~/release/REL.0.13$ cat /proc/cpuinfo
> processor : 0
> vendor_id : GenuineIntel
> cpu family : 6
> model : 2
> model name : QEMU Virtual CPU version 0.14.1
> stepping : 3
> cpu MHz : 2393.998
> cache size : 4096 KB
> fpu : yes
> fpu_exception : yes
> cpuid level : 4
> wp : yes
> flags : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pse36
> clflush mmx fxsr sse sse2 syscall nx lm up rep_good nopl pni cx16 popcnt
> hypervisor lahf_lm
> bogomips : 4787.99
> clflush size : 64
> cache_alignment : 64
> address sizes : 40 bits physical, 48 bits virtual
> power management:
>
> ronjpark@PSEProxy:~/release/REL.0.13$ cat /proc/meminfo
> MemTotal: 4057052 kB
> MemFree: 2651832 kB
> Buffers: 80984 kB
> Cached: 1100692 kB
> SwapCached: 3856 kB
> Active: 325744 kB
> Inactive: 910176 kB
> Active(anon): 48884 kB
> Inactive(anon): 5684 kB
> Active(file): 276860 kB
> Inactive(file): 904492 kB
> Unevictable: 0 kB
> Mlocked: 0 kB
> SwapTotal: 2095100 kB
> SwapFree: 2082688 kB
> Dirty: 4 kB
> Writeback: 0 kB
> AnonPages: 51356 kB
> Mapped: 15740 kB
> Shmem: 324 kB
> Slab: 66252 kB
> SReclaimable: 56796 kB
> SUnreclaim: 9456 kB
> KernelStack: 1160 kB
> PageTables: 4124 kB
> NFS_Unstable: 0 kB
> Bounce: 0 kB
> WritebackTmp: 0 kB
> CommitLimit: 4123624 kB
> Committed_AS: 176112 kB
> VmallocTotal: 34359738367 kB
> VmallocUsed: 28816 kB
> VmallocChunk: 34359707236 kB
> HardwareCorrupted: 0 kB
> HugePages_Total: 0
> HugePages_Free: 0
> HugePages_Rsvd: 0
> HugePages_Surp: 0
> Hugepagesize: 2048 kB
> DirectMap4k: 42996 kB
> DirectMap2M: 4151296 kB
> ronjpark@PSEProxy:~/release/REL.0.13$ uname -a
> Linux PSEProxy 2.6.38-8-server #42-Ubuntu SMP Mon Apr 11 03:49:04 UTC
> 2011 x86_64 x86_64 x86_64 GNU/Linux

The bottleneck is neither CPU nor memory. VM disk performance will be
bad. Any throughput you get on the virtual disk will degrade as each
concurrent upload client triggers reads and writes. This is one case
where you need a SAN, ZFS filesystem, or an SSD drive; configure with
large block size if files are >1GB. Even server class hard drives will
thrash and slow down everything with enough clients contending for the
disk. Remember, in relative time, if a cpu operation takes a second,
an operation on the disk takes one month, under ideal conditions, and
you are giving nginx less than ideal conditions.

Stefan Caunter
http://scaleengine.com/contact

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