From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Nick Piggin <npiggin@suse.de>
Cc: linuxppc-dev@ozlabs.org, Anton Blanchard <anton@samba.org>
Subject: Re: [PATCH 6/6] powerpc: Use lwsync for acquire barrier if CPU supports it
Date: Wed, 17 Feb 2010 23:12:34 +1100 [thread overview]
Message-ID: <1266408754.16346.280.camel@pasglop> (raw)
In-Reply-To: <20100217104153.GA7952@laptop>
> Yes I suppose the branch can be executed "non speculatively" before the
> lwsync is completed. Wheras the larx/stcwx will have to complete before
> the branch outcome can be known. I suppose probably not worthwhile
> avoiding the full IO sync by adding yet more crap to make this work.
>
> Thanks for putting my mind to rest though :)
>
> I'd still be interested to know how expensive the full sync is when you
> have a lot of IOs in flight.
>
> Question, are you going to do the hint and isync->lwsync thing for
> userspace as well? Too bad the kernel doesn't export synchronisation
> primitives to userspace...
We'd love to.... the vdso inherits from all the dynamic patching
features of the kernel and more...
It's really a matter of getting glibc to grok it, and doing so
efficiently (ie, not just having a function point in glibc, might be a
good use of the IFUNC stuff).
Cheers,
Ben.
next prev parent reply other threads:[~2010-02-17 12:12 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-10 10:57 [PATCH 1/6] powerpc: Use lwarx hint in spinlocks Anton Blanchard
2010-02-10 11:02 ` [PATCH 2/6] powerpc: Use lwarx/ldarx hint in bit locks Anton Blanchard
2010-02-10 11:03 ` [PATCH 3/6] powerpc: Convert open coded native hashtable bit lock Anton Blanchard
2010-02-10 11:04 ` [PATCH 4/6] powerpc: Rename LWSYNC_ON_SMP to PPC_RELEASE_BARRIER, ISYNC_ON_SMP to PPC_ACQUIRE_BARRIER Anton Blanchard
2010-02-10 11:07 ` [PATCH 5/6] powerpc: Fix lwsync patching code on 64bit Anton Blanchard
2010-02-10 11:10 ` [PATCH 6/6] powerpc: Use lwsync for acquire barrier if CPU supports it Anton Blanchard
2010-02-11 7:09 ` Nick Piggin
2010-02-17 9:43 ` Anton Blanchard
2010-02-17 10:41 ` Nick Piggin
2010-02-17 12:12 ` Benjamin Herrenschmidt [this message]
2010-02-16 4:22 ` Olof Johansson
2010-02-16 4:19 ` Benjamin Herrenschmidt
2010-02-16 6:07 ` Olof Johansson
2010-03-19 1:08 ` [PATCH 4/6] powerpc: Rename LWSYNC_ON_SMP to PPC_RELEASE_BARRIER, ISYNC_ON_SMP to PPC_ACQUIRE_BARRIER Nick Piggin
2010-03-19 1:36 ` Benjamin Herrenschmidt
2010-02-11 6:56 ` [PATCH 1/6] powerpc: Use lwarx hint in spinlocks Nick Piggin
2010-02-17 9:37 ` Anton Blanchard
2010-02-17 10:22 ` Nick Piggin
2010-02-16 4:16 ` Olof Johansson
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