Date: Fri, 22 Apr 2016 14:49:57 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Roman Peniaev <r.peniaev@gmail.com>, intel-gfx@lists.freedesktop.org,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Toshi Kani <toshi.kani@hp.com>, Shawn Lin <shawn.lin@rock-chips.com>,
        linux-mm@kvack.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm/vmalloc: Keep a separate lazy-free list
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On Fri, 15 Apr 2016 12:14:31 +0100 Chris Wilson <chris@chris-wilson.co.uk> wrote:

> > > purge_fragmented_blocks() manages per-cpu lists, so that looks safe
> > > under its own rcu_read_lock.
> > >
> > > Yes, it looks feasible to remove the purge_lock if we can relax sync.
> > 
> > what is still left is waiting on vmap_area_lock for !sync mode.
> > but probably is not that bad.
> 
> Ok, that's bit beyond my comfort zone with a patch to change the free
> list handling. I'll chicken out for the time being, atm I am more
> concerned that i915.ko may call set_page_wb() frequently on individual
> pages.

Nick Piggin's vmap rewrite.  20x (or more) faster. 
https://lwn.net/Articles/285341/

10 years ago, never finished.