1) Gazelle is a fast PSGI/Plack HTTP server written in Perl and C code. 2) Benchmarks show it can handle 3x more requests per second than other servers for simple applications. 3) Its speed comes from optimizations like using accept4, writev system calls, and being written mostly in fast C code via XS.

1. Gazelle
Plack Handler for performance freaks
Yokohama.pm #12
Masahiro Nagano (kazeburo)
https://www.!ickr.com/photos/ckindel/424610604/

2. Me
• 長野雅広 (Masahiro Nagano)
• @kazeburo
• CPAN: KAZEBURO / github: kazeburo
• 横浜市西区在住
• ISUCON 2013,2014 優勝

3. Gazelle

4. Gazelle #とは
• Plack Handler / PSGI Server
• HTTP/1.0 Web Server
• Preforking Architecture
• Suitable for running application servers
behind a reverse proxy
• Starlet compatible / hot deploy
• Fast Fast Fast

5. “Hello World”
130,000
97,500
req/sec nginx starman Starlet Gazelle
65,000
32,500
0
106,028
62,069
33,300
127,462
3x Faster!!
than starman

6. “counter.psgi”
110,000
82,500
55,000
27,500
0
42,285
106,028
28,292
62,069
20,100
33,300
hello world counter.psgi
req/sec
starman Starlet Gazelle

7. ISUCON4 Quali!er
45,000
33,750
Score 予選通過ラインstarman Starlet Gazelle
22,500
11,250
39,776 42,813 44,764 37,808
「ISUCON4 予選でアプリケーションを変更せずに予選通過ラインを突破するの術」
に若干変更を加えたバージョン

8. Gazelle はなぜ速い
• Only Support HTTP/1.0 and does not
support KeepAlive. It make code very simple
• Mostly written in XS
• Ultra fast HTTP processing using
picohttpparser
• Use accept4(2)
• Use writev(2) for output responses

9. Simple HTTP/1.0 GET
accept4(2)
read(2)
parse_header
poll(2)
complete?
OK
execute app
writev(2)
poll(2)
written?
close(2)
No
OK No

10. Mostly written in XS
accept4(2)
read(2)
parse_header
poll(2)
complete?
OK
execute app
writev(2)
poll(2)
written?
close(2)
No
OK No
XS
XS

11. Perl code using XS
while (1) {
if ( my ($fd, $buf, $env) = accept_psgi(
fileno($listen_sock), $timeout, $listen_sock_is_tcp,
$host || 0, $port || 0
) ) {
my $guard = guard { close_client($fd) };
$res = Plack::Util::run_app $app, $env;
my $status_code = $res->[0];
my $headers = $res->[1];
my $body = $res->[2];
write_psgi_response($fd, $timeout, $status_code, $headers, $body);
}

12. Perl code using XS
while (1) {
if ( my ($fd, $buf, $env) = accept_psgi(
fileno($listen_sock), $timeout, $listen_sock_is_tcp,
$host || 0, $port || 0
) ) {
my $guard = guard { close_client($fd) };
$res = Plack::Util::run_app $app, $env;
my $status_code = $res->[0];
my $headers = $res->[1];
my $body = $res->[2];
write_psgi_response($fd, $timeout, $status_code, $headers, $body);
}

13. picohttpparser
• created by kazuho-san
• used in H2O and HTTP::Parser::XS

14. 必読
http://blog.kazuhooku.com/2014/11/the-internals-h2o-or-how-to-write-fast.html

15. accept4(2)
• Required Linux >= 2.6.28
• Set FD_CLOEXEC and O_NONBLOCK in
one system call

16. accept4(2)
int
_accept(int fileno, struct sockaddr *addr, unsigned int addrlen) {
int fd;
#ifdef SOCK_NONBLOCK
fd = accept4(fileno, addr, &addrlen, SOCK_CLOEXEC|SOCK_NONBLOCK);
#else
fd = accept(fileno, addr, &addrlen);
fcntl(fd, F_SETFD, FD_CLOEXEC);
fcntl(fd, F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK);
#endif
return fd;
}

17. accept4(2)
13:51:26.755628 accept(4, {sa_family=AF_INET, sin_port=htons(42828),
sin_addr=inet_addr("127.0.0.1")}, [16]) = 5
13:51:27.324951 fcntl(5, F_SETFD, FD_CLOEXEC) = 0
13:51:27.325014 fcntl(5, F_GETFL) = 0x2 (flags O_RDWR)
13:51:27.325067 fcntl(5, F_SETFL, O_RDWR|O_NONBLOCK) = 0
13:51:27.325117 read(5, "GET / HTTP/1.1rnUser-Agent:"..., 16384) = 155
13:51:27.325200 setsockopt(5, SOL_TCP, TCP_NODELAY, [1], 4) = 0
13:52:17.946622 accept4(4, {sa_family=AF_INET, sin_port=htons(42835),
sin_addr=inet_addr("127.0.0.1")}, [16], SOCK_CLOEXEC|SOCK_NONBLOCK) = 5
13:52:18.505428 read(5, "GET / HTTP/1.1rnUser-Agent:”..., 16384) = 155
13:52:18.505519 setsockopt(5, SOL_TCP, TCP_NODELAY, [1], 4) = 0

18. writev
• write multiple buffer to a fd in one
system call
• reduce memory copy or system calls

19. ex. memory copy
#perl
my $header = ["Server"=>"gazelle","Content-Type"=>"text/plain",...];
#xs
char buf[512];
while ( i < av_len(headers) + 1 ) {
key = SvPV_nolen(*av_fetch(headers,i++,0));
strcat(buf, key);
strcat(buf, ": ");
val = SvPV_nolen(*av_fetch(headers,i++,0));
strcat(buf, val);
strcat(buf, "rn");
}
write(fd, buf, sizeof(buf)-1);
Too many
memory copy
cause system
overhead

20. ex. write write write
#perl
my $header = ["Server"=>"gazelle","Content-Type"=>"text/plain"];
#xs
while ( i < av_len(headers) + 1 ) {
key = SvPV(*av_fetch(headers,i++,0),&len);
write(fd, key, len);
write(fd, ": ", sizeof(“: ”) - 1);
val = SvPV(*av_fetch(headers,i++,0),&len);
write(fd, val, len);
write(fd, "rn", sizeof(“rn”) - 1);
}
Too many
write(2)
increase latency
of network

21. writev(2)
#perl
my $header = ["Server"=>"gazelle","Content-Type"=>"text/plain"];
#xs
struct iovec v[av_len(headers)+1)*2 + 10];
iovcnt = 0;
while ( i < av_len(headers) + 1 ) {
key = SvPV(*av_fetch(headers,i++,0),&len);
iovcnt++;
v[iovcnt].iov_base = key;
v[iovcnt].iov_len = len;
iovcnt++;
v[iovcnt].iov_base = “: ”;
no memory copy
v[iovcnt].iov_len = sizeof(“: ”) - 1;
one system call
...
}
writev(fd, v, iovcnt);

22. writev(2)
plackup -s Gazelle -e 'sub{[200,["Content-Type"=>"text/plain"],
["xxx","xxx","yyy","yyy","zzzz","n"]]}'
writev(5, [{"HTTP/1.0 200 OKrnConnection: closernServer: gazeller
n", 53}, {"Content-Type", 12}, {": ", 2}, {"text/plain", 10}, {"rn",
2}, {"Date: Fri, 28 Nov 2014 04:38:08 GMTrnrn", 39}, {"xxx", 3},
{"xxx", 3}, {"yyy", 3}, {"yyy", 3}, {"zzzz", 4}, {"n", 1}], 12) = 135

23. 高速なサーバを書くには
• write XS, minimize Perl code
• reduce system calls
• Zero Copy

24. 高速なAppサーバって必要なの？
• ISUCON :)
• Social Games, AdTech, SNS
• High optimized applications
• few msec ~ few tens of msec
• Several hundreds of request/sec/host
• 1PVあたりの利益が小さいサービス

25. Gazelleの実績
• livedoor Blog
• 2500万req/day/host
• Starletからの移行でCPU使用率
1%~3%さがった

26. ぜひお使い下さい
https://www.!ickr.com/photos/superformosa/9057428400/