From: Tom Lane <tgl@sss.pgh.pa.us>
To: Stephen Frost <sfrost@snowman.net>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: David Steele <david@pgmasters.net>
Cc: Joe Conway <mail@joeconway.com>
Cc: Magnus Hagander <magnus@hagander.net>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Nico Williams <nico@cryptonector.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Robbie Harwood <rharwood@redhat.com>
Subject: Re: [PATCH v20] GSSAPI encryption support
Date: Thu, 04 Apr 2019 13:05:29 -0400
Message-ID: <18056.1554397529@sss.pgh.pa.us> (raw)
In-Reply-To: <20190404162452.GM6197@tamriel.snowman.net>
References: <7b7035e0-3691-ca63-0957-25d17dc11514@2ndquadrant.com>
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<5406.1554388830@sss.pgh.pa.us>
<20190404144818.GI6197@tamriel.snowman.net>
<5945.1554389568@sss.pgh.pa.us>
<20190404150054.GJ6197@tamriel.snowman.net>
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<20190404152439.GK6197@tamriel.snowman.net>
<8476.1554391968@sss.pgh.pa.us>
<15827.1554394584@sss.pgh.pa.us>
<20190404162452.GM6197@tamriel.snowman.net>
Stephen Frost <sfrost@snowman.net> writes:
> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
>> Watching the test logs, I see that essentially all the time on the RHEL6
>> machine is consumed by the two
>> # Running: /usr/sbin/kdb5_util create -s -P secret0
>> steps. Is there a case for merging the two scripts so we only have to
>> do that once? Maybe not, if nobody else sees this.
> I do think that mergeing them would be a good idea and I can look into
> that, though at least locally that step takes less than a second.. I
> wonder if you might strace (or whatever is appropriate) that kdb5_util
> and see what's taking so long. I seriously doubt it's the actual
> kdb5_util code and strongly suspect it's some kernel call.
"strace -r" pins the blame pretty firmly on /dev/random:
0.000076 open("/dev/random", O_RDONLY) = 3
0.000227 fcntl(3, F_SETFD, FD_CLOEXEC) = 0
0.000061 fstat(3, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 8), ...}) = 0
0.000068 read(3, "\336&\301\310V\344q\217\264-\262\320w-", 64) = 14
0.000091 read(3, "\326\353I\371$\361", 50) = 6
15.328306 read(3, "\214\301\313]I\325", 44) = 6
17.418929 read(3, "z\251\37\275\365\24", 38) = 6
13.366997 read(3, "6\257I\315f\3", 32) = 6
11.457994 read(3, "\370\275\2765\31(", 26) = 6
23.472194 read(3, "\226\r\314\373\2014", 20) = 6
11.746848 read(3, "\335\336BR\30\322", 14) = 6
20.823940 read(3, "\366\214\r\211\0267", 8) = 6
14.429214 read(3, ",g", 2) = 2
15.494835 close(3) = 0
There's no other part of the trace that takes more than ~ 0.1s.
So this boils down to the old bugaboo about how much entropy
there really is in /dev/random.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, sfrost@snowman.net, peter.eisentraut@2ndquadrant.com, alvherre@2ndquadrant.com, david@pgmasters.net, mail@joeconway.com, magnus@hagander.net, michael@paquier.xyz, nico@cryptonector.com, rharwood@redhat.com
Subject: Re: [PATCH v20] GSSAPI encryption support
In-Reply-To: <18056.1554397529@sss.pgh.pa.us>
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