From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: Florian Weimer <fweimer@redhat.com>,
Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Cc: Wilco Dijkstra via Libc-alpha <libc-alpha@sourceware.org>,
"naohirot@fujitsu.com" <naohirot@fujitsu.com>
Subject: Re: [PATCH 0/5] Added optimized memcpy/memmove/memset for A64FX
Date: Tue, 4 May 2021 10:38:42 +0000 [thread overview]
Message-ID: <VE1PR08MB5599D690BF8549F57A9E578E835A9@VE1PR08MB5599.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <87a6pan6pr.fsf@oldenburg.str.redhat.com>
Hi Florian,
> I find this discussion extremely worrisome. If bti c does not behave
> like a nop, then we need a new AArch64 ABI variant to enable BTI.
>
> That being said, a distribution with lots of bti c instructions in
> binaries seems to run on A64FX CPUs, so I'm not sure what is going on.
NOP-space instructions should take no time or execution resources.
From Naohiro's graphs I estimate A64FX takes around 30 cycles per BTI
instruction - that's clearly "not behaving like a NOP". That would cause a
significant performance degradation if BTI is enabled in a distro.
Cheers,
Wilco
next prev parent reply other threads:[~2021-05-04 10:38 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 12:52 Wilco Dijkstra
2021-04-12 18:53 ` Florian Weimer
2021-04-13 12:07 ` naohirot
2021-04-14 16:02 ` Wilco Dijkstra
2021-04-15 12:20 ` naohirot
2021-04-20 16:00 ` Wilco Dijkstra
2021-04-27 11:58 ` naohirot
2021-04-29 15:13 ` Wilco Dijkstra
2021-04-30 15:01 ` Szabolcs Nagy
2021-04-30 15:23 ` Wilco Dijkstra
2021-04-30 15:30 ` Florian Weimer
2021-04-30 15:40 ` Wilco Dijkstra
2021-05-04 7:56 ` Szabolcs Nagy
2021-05-04 10:17 ` Florian Weimer
2021-05-04 10:38 ` Wilco Dijkstra [this message]
2021-05-04 10:42 ` Szabolcs Nagy
2021-05-04 11:07 ` Florian Weimer
2021-05-06 10:01 ` naohirot
2021-05-06 14:26 ` Szabolcs Nagy
2021-05-06 15:09 ` Florian Weimer
2021-05-06 17:31 ` Wilco Dijkstra
2021-05-07 12:31 ` naohirot
2021-04-19 2:51 ` naohirot
2021-04-19 14:57 ` Wilco Dijkstra
2021-04-21 10:10 ` naohirot
2021-04-21 15:02 ` Wilco Dijkstra
2021-04-22 13:17 ` naohirot
2021-04-23 0:58 ` naohirot
2021-04-19 12:43 ` naohirot
2021-04-20 3:31 ` naohirot
2021-04-20 14:44 ` Wilco Dijkstra
2021-04-27 9:01 ` naohirot
2021-04-20 5:49 ` naohirot
2021-04-20 11:39 ` Wilco Dijkstra
2021-04-27 11:03 ` naohirot
2021-04-23 13:22 ` naohirot
-- strict thread matches above, loose matches on Subject: below --
2021-03-17 2:28 Naohiro Tamura
2021-03-29 12:03 ` Szabolcs Nagy
2021-05-10 1:45 ` naohirot
2021-05-14 13:35 ` Szabolcs Nagy
2021-05-19 0:11 ` naohirot
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