From: Michael Ellerman <mpe@ellerman.id.au>
To: Andrey Abramov <st5pub@yandex.ru>, vgupta <vgupta@synopsys.com>,
benh <benh@kernel.crashing.org>, paulus <paulus@samba.org>,
tglx <tglx@linutronix.de>, mingo <mingo@redhat.com>,
bp <bp@alien8.de>, hpa <hpa@zytor.com>, x86 <x86@kernel.org>,
mark <mark@fasheh.com>, jlbec <jlbec@evilplan.org>,
richard <richard@nod.at>, dedekind1 <dedekind1@gmail.com>,
"adrian.hunter" <adrian.hunter@intel.com>,
gregkh <gregkh@linuxfoundation.org>,
"naveen.n.rao" <naveen.n.rao@linux.vnet.ibm.com>,
jpoimboe <jpoimboe@redhat.com>,
Dave Chinner <dchinner@redhat.com>,
"darrick.wong" <darrick.wong@oracle.com>,
"ard.biesheuvel" <ard.biesheuvel@linaro.org>,
George Spelvin <lkml@sdf.org>,
linux-snps-arc <linux-snps-arc@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
ocfs2-devel <ocfs2-devel@oss.oracle.com>,
linux-mtd <linux-mtd@lists.infradead.org>,
sfr <sfr@canb.auug.org.au>
Cc: malat <malat@debian.org>,
"yamada.masahiro" <yamada.masahiro@socionext.com>,
npiggin <npiggin@gmail.com>
Subject: Re: [PATCH v2 2/5] powerpc: module_[32|64].c: replace swap function with built-in one
Date: Mon, 01 Apr 2019 22:08:30 +1100 [thread overview]
Message-ID: <87v9zyoudt.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <14019281554057359@sas1-87f9feb8d943.qloud-c.yandex.net>
Andrey Abramov <st5pub@yandex.ru> writes:
> Replace relaswap with built-in one, because relaswap
> does a simple byte to byte swap.
I replied to v1 with an ack, which stands, this is just a clarification.
> Since Spectre mitigations have made indirect function calls more
> expensive, and the default simple byte copies swap is implemented
> without them, an "optimized" custom swap function is now
> a waste of time as well as code.
Spectre mitigations don't necessarily slow down indirect function calls
on all arches or in all configurations on all arches, so that
justification is a bit dubious.
That's not really a problem for this patch, because the existing
overhead of the function call is probably already enough to rival the
cost of the 24 byte copy.
cheers
next prev parent reply other threads:[~2019-04-01 11:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-31 18:28 [PATCH v2 0/5] simple sort swap function improvements Andrey Abramov
2019-03-31 18:31 ` [PATCH v2 1/5] arch/arc: unwind.c: replace swap function with built-in one Andrey Abramov
2019-04-01 17:53 ` Vineet Gupta
2019-03-31 18:35 ` [PATCH v2 2/5] powerpc: module_[32|64].c: " Andrey Abramov
2019-04-01 11:08 ` Michael Ellerman [this message]
2019-03-31 18:42 ` [PATCH v2 3/5] ocfs2: dir, refcounttree, xattr: replace swap functions " Andrey Abramov
2019-03-31 18:47 ` [PATCH v2 4/5] ubifs: find.c: replace swap function " Andrey Abramov
2019-03-31 18:52 ` [PATCH v2 5/5] Lib: sort.h: replace int size with size_t size in the swap function Andrey Abramov
2019-04-01 9:35 ` Andy Shevchenko
2019-04-01 9:56 ` George Spelvin
2019-04-01 10:28 ` Andy Shevchenko
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