From: "Theodore Ts'o" <tytso@mit.edu>
To: "Stephan Müller" <smueller@chronox.de>
Cc: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org
Subject: Re: [PATCH 4/8] random: remove unused branch in hot code path
Date: Tue, 17 Jan 2017 23:35:36 -0500 [thread overview]
Message-ID: <20170118043536.aeqmxfthmx4h33g7@thunk.org> (raw)
In-Reply-To: <3380804.uZWydldqLU@positron.chronox.de>
On Tue, Dec 27, 2016 at 11:40:23PM +0100, Stephan Müller wrote:
> The variable ip is defined to be a __u64 which is always 8 bytes on any
> architecture. Thus, the check for sizeof(ip) > 4 will always be true.
>
> As the check happens in a hot code path, remove the branch.
The fact that it's a hot code path means the compiler will optimize it
out, so the fact that it's on the hot code path is irrelevant. The
main issue is that on platforms with a 32-bit IP's, ip >> 32 will
always be zero. It might be that we can just do this via
#if BITS_PER_LONG == 32
...
#else
...
#endif
I'm not sure that works for all platforms, though. More research is
needed...
- Ted
next prev parent reply other threads:[~2017-01-18 4:35 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-27 22:38 [PATCH 0/8] random: cleanup of code after removal of nonblocking pool Stephan Müller
2016-12-27 22:39 ` [PATCH 1/8] random: remove stale maybe_reseed_primary_crng Stephan Müller
2016-12-27 22:39 ` [PATCH 2/8] random: remove stale urandom_init_wait Stephan Müller
2016-12-27 22:39 ` [PATCH 3/8] random: trigger random_ready callback upon crng_init == 1 Stephan Müller
2017-01-18 4:12 ` Theodore Ts'o
2017-01-18 17:09 ` Stephan Müller
2016-12-27 22:40 ` [PATCH 4/8] random: remove unused branch in hot code path Stephan Müller
2017-01-18 4:35 ` Theodore Ts'o [this message]
2017-04-27 11:23 ` Geert Uytterhoeven
2016-12-27 22:40 ` [PATCH 5/8] random: remove variable limit Stephan Müller
2016-12-27 22:41 ` [PATCH 6/8] random: fix comment for unused random_min_urandom_seed Stephan Müller
2016-12-27 22:41 ` [PATCH 7/8] random: remove noop function call to xfer_secondary_pool Stephan Müller
2017-01-18 16:10 ` Theodore Ts'o
2016-12-27 22:42 ` [PATCH 8/8] random: move FIPS continuous test to output functions Stephan Müller
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