From: Wilco Dijkstra via Libc-alpha <libc-alpha@sourceware.org>
To: "naohirot@fujitsu.com" <naohirot@fujitsu.com>
Cc: Szabolcs Nagy <Szabolcs.Nagy@arm.com>,
'GNU C Library' <libc-alpha@sourceware.org>
Subject: Re: [PATCH 0/5] Added optimized memcpy/memmove/memset for A64FX
Date: Tue, 20 Apr 2021 16:00:32 +0000 [thread overview]
Message-ID: <VE1PR08MB5599FC008D30BD29F09972BA83489@VE1PR08MB5599.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <TYAPR01MB6025DB73491ACFBC0411E0A0DF4D9@TYAPR01MB6025.jpnprd01.prod.outlook.com>
Hi Naohiro,
> Yes, I observed that just " hint #0x22" is inserted.
> The benchtest results show that the A64FX performance of size less than 100B with
> BTI is slower than ASIMD, but without BTI is faster than ASIMD.
> And the A64FX performance of 512B with BTI 4Gbps/sec slower than without BTI.
That's unfortunate - it seems like the hint is very slow, maybe even serializing...
We can work around if for now in GLIBC, but at some point distros will start to insert
BTI instructions by default, and then the performance hit will be bad.
> So if distinct degradation happens only on A64FX, I'd like to add another
> ENTRY macro in sysdeps/aarch64/sysdep.h such as:
I think the best option for now is to change BTI_C into NOP if AARCH64_HAVE_BTI
is not set. This avoids creating alignment issues in existing code (which is written
to assume the hint is present) and works for all string functions.
Cheers,
Wilco
next prev parent reply other threads:[~2021-04-20 16:01 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 12:52 [PATCH 0/5] Added optimized memcpy/memmove/memset for A64FX Wilco Dijkstra via Libc-alpha
2021-04-12 18:53 ` Florian Weimer
2021-04-13 12:07 ` naohirot
2021-04-14 16:02 ` Wilco Dijkstra via Libc-alpha
2021-04-15 12:20 ` naohirot
2021-04-20 16:00 ` Wilco Dijkstra via Libc-alpha [this message]
2021-04-27 11:58 ` naohirot
2021-04-29 15:13 ` Wilco Dijkstra via Libc-alpha
2021-04-30 15:01 ` Szabolcs Nagy via Libc-alpha
2021-04-30 15:23 ` Wilco Dijkstra via Libc-alpha
2021-04-30 15:30 ` Florian Weimer via Libc-alpha
2021-04-30 15:40 ` Wilco Dijkstra via Libc-alpha
2021-05-04 7:56 ` Szabolcs Nagy via Libc-alpha
2021-05-04 10:17 ` Florian Weimer via Libc-alpha
2021-05-04 10:38 ` Wilco Dijkstra via Libc-alpha
2021-05-04 10:42 ` Szabolcs Nagy via Libc-alpha
2021-05-04 11:07 ` Florian Weimer via Libc-alpha
2021-05-06 10:01 ` naohirot
2021-05-06 14:26 ` Szabolcs Nagy via Libc-alpha
2021-05-06 15:09 ` Florian Weimer via Libc-alpha
2021-05-06 17:31 ` Wilco Dijkstra via Libc-alpha
2021-05-07 12:31 ` naohirot
2021-04-19 2:51 ` naohirot
2021-04-19 14:57 ` Wilco Dijkstra via Libc-alpha
2021-04-21 10:10 ` naohirot
2021-04-21 15:02 ` Wilco Dijkstra via Libc-alpha
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 via Libc-alpha
2021-04-27 9:01 ` naohirot
2021-04-20 5:49 ` naohirot
2021-04-20 11:39 ` Wilco Dijkstra via Libc-alpha
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 via Libc-alpha
2021-05-10 1:45 ` naohirot
2021-05-14 13:35 ` Szabolcs Nagy via Libc-alpha
2021-05-19 0:11 ` naohirot
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