different Memory consumption for H1 and H2

[Muhui Jiang]

Hi

Recently, I did an experiment to test the memory consumption of nginx. I
request a large static zip file. I explored the debug information of nginx.

For H2, below is a part of the log, I noticed that every time server will
allocate 65536 bytes, I increase the connection number, I noticed that the
server's memory consumption will reach to a threshhold and then increase
very slowly:
2017/05/11 04:54:20 [debug] 29451#0: *10499 http2:1 HEADERS frame
00000000026155F0 was sent
2017/05/11 04:54:20 [debug] 29451#0: *10499 http2 frame sent:
00000000026155F0 sid:1 bl:1 len:119
2017/05/11 04:54:20 [debug] 29451#0: *10499 http output filter
"/image/test.zip?"
2017/05/11 04:54:20 [debug] 29451#0: *10499 http copy filter:
"/image/test.zip?"
2017/05/11 04:54:20 [debug] 29451#0: *10499 malloc: 0000000002699A80:65536
2017/05/11 04:54:20 [debug] 29451#0: *10499 read: 14, 0000000002699A80,
65536, 0
2017/05/11 04:54:20 [debug] 29451#0: *10499 http postpone filter
"/image/test.zip?" 0000000002616098
2017/05/11 04:54:20 [debug] 29451#0: *10499 write new buf t:1 f:1
0000000002699A80, pos 0000000002699A80, size: 65536 file: 0, size: 65536
2017/05/11 04:54:20 [debug] 29451#0: *10499 http write filter: l:0 f:1
s:65536
2017/05/11 04:54:20 [debug] 29451#0: *10499 http write filter limit 0
2017/05/11 04:54:20 [debug] 29451#0: *10499 http2:1 create DATA frame
00000000026155F0: len:1 flags:0
2017/05/11 04:54:20 [debug] 29451#0: *10499 http2 frame out:
00000000026155F0 sid:1 bl:0 len:1
2017/05/11 04:54:20 [debug] 29451#0: *10499 SSL buf copy: 9
2017/05/11 04:54:20 [debug] 29451#0: *10499 SSL buf copy: 1
2017/05/11 04:54:20 [debug] 29451#0: *10499 SSL to write: 138
2017/05/11 04:54:20 [debug] 29451#0: *10499 SSL_write: 138
2017/05/11 04:54:20 [debug] 29451#0: *10499 http2:1 DATA frame
00000000026155F0 was sent
2017/05/11 04:54:20 [debug] 29451#0: *10499 http2 frame sent:
00000000026155F0 sid:1 bl:0 len:1
2017/05/11 04:54:20 [debug] 29451#0: *10499 http write filter
00000000026160A8
2017/05/11 04:54:20 [debug] 29451#0: *10499 malloc: 00000000026A9A90:65536

For H/1.1, below is a part of the debug log, no malloc is noticed during
the send file process. And even when I increase the connection number to a
very large value, the result shows nginx's memory consumption is still very
low. :
2017/05/11 22:29:06 [debug] 29451#0: *11015 http run request:
"/image/test.zip?"
2017/05/11 22:29:06 [debug] 29451#0: *11015 http writer handler:
"/image/test.zip?"
2017/05/11 22:29:06 [debug] 29451#0: *11015 http output filter
"/image/test.zip?"
2017/05/11 22:29:06 [debug] 29451#0: *11015 http copy filter:
"/image/test.zip?"
2017/05/11 22:29:06 [debug] 29451#0: *11015 http postpone filter
"/image/test.zip?" 0000000000000000
2017/05/11 22:29:06 [debug] 29451#0: *11015 write old buf t:0 f:1
0000000000000000, pos 0000000000000000, size: 0 file: 72470952, size: 584002
2017/05/11 22:29:06 [debug] 29451#0: *11015 http write filter: l:1 f:0
s:584002
2017/05/11 22:29:06 [debug] 29451#0: *11015 http write filter limit 0
2017/05/11 22:29:06 [debug] 29451#0: *11015 sendfile: @72470952 584002
2017/05/11 22:29:06 [debug] 29451#0: *11015 sendfile: 260640 of 584002
@72470952
2017/05/11 22:29:06 [debug] 29451#0: *11015 http write filter
0000000002670F70
2017/05/11 22:29:06 [debug] 29451#0: *11015 http copy filter: -2
"/image/test.zip?"
2017/05/11 22:29:06 [debug] 29451#0: *11015 http writer output filter: -2,
"/image/test.zip?"
2017/05/11 22:29:06 [debug] 29451#0: *11015 event timer: 3, old:
1494513006630, new: 1494513006763

Hope to get your comments and what are the difference of nginx's memory
allocation mechanisms between HTTP/2.0 and HTTP/1.1. Many Thanks

Regards
Muhui
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