Messages in this thread | | | Subject | Re: jitterentropy: `jent_mod_init()` takes 17 ms | From | Paul Menzel <> | Date | Tue, 10 Nov 2020 10:37:02 +0100 |
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Dear Stephan,
Thank you for the quick reply.
Am 10.11.20 um 10:25 schrieb Stephan Mueller: > Am Montag, 9. November 2020, 20:31:02 CET schrieb Paul Menzel:
>> By mistake I built `XFRM_ESP` into the Linux kernel, resulting in >> >> CONFIG_CRYPTO_SEQIV=y >> CONFIG_CRYPTO_ECHAINIV=y >> >> and also the Jitterentropy RNG to be built in. >> >> CRYPTO_JITTERENTROPY=y >> >> So, on the Asus F2A85-M PRO starting Linux 4.10-rc3 with >> `initcall_debug`, the init method is run unconditionally, and it takes >> 17.5 ms, which is over ten percent of the overall 900 ms the Linux > > Hm, 17.5 / 900 = 2%, or am I missing something?
Indeed, that is embarrassing. My bad.
>> kernel needs until loading the init process. >> >> [ 0.300544] calling jent_mod_init+0x0/0x2c @ 1 >> [ 0.318438] initcall jent_mod_init+0x0/0x2c returned 0 after 17471 usecs >> >> Looking at the output of systemd-bootchart, it looks like, that this >> indeed delayed the boot a little, as the other init methods seem to be >> ordered after it. >> >> I am now building it as a module, but am wondering if the time can be >> reduced to below ten milliseconds. > > What you see is the test whether the Jitter RNG has a proper noise source. The > function jent_entropy_init() is the cause of the operation. It performs 1024 > times a test to validate the appropriateness of the noise source. You can > adjust that with the TESTLOOPCOUNT in this function. But I am not sure > adjusting is a wise course of action.
Out of curiosity, why 1024 and not, for example, 128 or 2048? Is there some statistics behind it?
Kind regards,
Paul
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