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Date: Thu, 16 Jul 2015 00:30:27 -0700
From: Dave Hansen <dave.hansen@linux.intel.com>
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To: Jan Kara <jack@suse.cz>, Oleg Nesterov <oleg@redhat.com>
CC: Al Viro <viro@zeniv.linux.org.uk>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Daniel Wagner <daniel.wagner@bmw-carit.de>,
        Davidlohr Bueso <dave@stgolabs.net>, Ingo Molnar <mingo@redhat.com>,
        Tejun Heo <tj@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC 0/4] change sb_writers to use percpu_rw_semaphore
References: <20150713212536.GA13855@redhat.com> <20150714104810.GB24369@quack.suse.cz> <20150714133731.GA24837@redhat.com> <55A57C50.1080406@linux.intel.com> <20150714212249.GA18441@redhat.com> <55A581F9.3090507@linux.intel.com> <20150715064705.GA22609@quack.suse.cz> <20150715181920.GA1797@redhat.com> <20150716072654.GE22847@quack.suse.cz>
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On 07/16/2015 12:26 AM, Jan Kara wrote:
> So Dave's patches would go in only in the next merge window anyway so we
> still have like two-three weeks to decide which patchset to take. If you
> think it will take you longer, then merging Dave's patches makes some sense
> although I personally don't think the issue is so important that we have to
> fix it ASAP and eventual delay of one more release would be OK for me.

I thought of one more thing.

Oleg's patches are fast in the uncontended case.  My testing of his code
so far was all single-threaded.  Will it slow down if we throw a bunch
of threads at it an see contention?  I don't think my RCU approach will.

I can benchmark in the next few days on a larger machine.