From: fgenfb@yahoo•com (Harm Hanemaaijer)
To: linux-arm-kernel@lists•infradead.org
Subject: Call for testing/opinions: Optimized memset/memcpy
Date: Sat, 13 Jul 2013 21:51:18 +0000 (UTC) [thread overview]
Message-ID: <loom.20130713T232124-511@post.gmane.org> (raw)
In-Reply-To: 20130713172445.GL32054@1wt.eu
Willy Tarreau <w <at> 1wt.eu> writes:
> OK I've run bench.script on the following platforms :
Thanks, that's incredibly helpful!
Note that Thumb2 mode usually doesn't do much in synthetic benchmarks,
because the benchmark code will fit into the L1 instruction cache; the
benefit of Thumb2 happens in real-world usage when the active code
footprint becomes larger.
To summarize, memset seems to be in good shape and also the "fast path"
for common word-aligned memcpy of size <= 256 seems to be working well.
However, the copy_page and memcpy results for larger sizes seem to suggest
that the prefetch strategy isn't working well on these platforms. Note also
that on the quad core the existing copy_page is also highly sub-optimal.
Fixing the preload strategy for these platforms may simply be a case of
changing the configurable constant PREFETCH_DISTANCE from 3 to 2 (from an
offset of 192 bytes to 128 bytes), which more closely mimics the original
kernel memcpy. I have added PREFETCH_DISTANCE as a configurable parameter
in the Makefile in the latest version of test-arm-kernel-memcpy. It will
be interesting to see the results of testing with a PREFETCH_DISTANCE
of 2 especially on the quad-core platform or a similar one.
next prev parent reply other threads:[~2013-07-13 21:51 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-13 15:51 Call for testing/opinions: Optimized memset/memcpy Harm Hanemaaijer
2013-07-13 16:48 ` Dr. David Alan Gilbert
2013-07-13 21:13 ` Harm Hanemaaijer
2013-07-15 13:15 ` Catalin Marinas
2013-07-14 11:19 ` Harm Hanemaaijer
2013-07-14 11:32 ` Dr. David Alan Gilbert
2013-07-14 11:37 ` Ard Biesheuvel
2013-07-14 13:13 ` Russell King - ARM Linux
2013-07-14 13:33 ` Harm Hanemaaijer
2013-07-14 14:09 ` Ard Biesheuvel
2013-07-14 14:32 ` Russell King - ARM Linux
2013-07-13 17:24 ` Willy Tarreau
2013-07-13 21:51 ` Harm Hanemaaijer [this message]
2013-07-14 6:13 ` Willy Tarreau
2013-07-14 11:00 ` Harm Hanemaaijer
2013-07-14 13:09 ` Russell King - ARM Linux
2013-07-14 13:59 ` Harm Hanemaaijer
2013-07-14 15:21 ` Siarhei Siamashka
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