linux-kernel - Re: [PATCH 1/4] mm, vmscan: Batch removal of mappings under a single lock during reclaim

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Message-ID: <20160916132506.GB5035@twins.programming.kicks-ass.net>
Date:   Fri, 16 Sep 2016 15:25:06 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     LKML <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>,
        Dave Chinner <david@...morbit.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ying Huang <ying.huang@...el.com>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH 1/4] mm, vmscan: Batch removal of mappings under a single
 lock during reclaim

On Fri, Sep 09, 2016 at 10:59:32AM +0100, Mel Gorman wrote:
> Pages unmapped during reclaim acquire/release the mapping->tree_lock for
> every single page. There are two cases when it's likely that pages at the
> tail of the LRU share the same mapping -- large amounts of IO to/from a
> single file and swapping. This patch acquires the mapping->tree_lock for
> multiple page removals.

So, once upon a time, in a galaxy far away,..  I did a concurrent
pagecache patch set that replaced the tree_lock with a per page bit-
spinlock and fine grained locking in the radix tree.

I know the mm has changed quite a bit since, but would such an approach
still be feasible?

I cannot seem to find an online reference to a 'complete' version of
that patch set, but I did find the OLS paper on it and I did find some
copies on my local machines.