linux-kernel - Re: [PATCH 1/3] i915/gvt: seperate tracked MMIO table from handlers.c

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Date:   Tue, 9 Nov 2021 11:58:40 +0100
From:   "hch@....de" <hch@....de>
To:     "Wang, Zhi A" <zhi.a.wang@...el.com>
Cc:     "hch@....de" <hch@....de>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Zhi Wang <zhi.wang.linux@...il.com>,
        "joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        "Vivi, Rodrigo" <rodrigo.vivi@...el.com>,
        "zhenyuw@...ux.intel.com" <zhenyuw@...ux.intel.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "intel-gvt-dev@...ts.freedesktop.org" 
        <intel-gvt-dev@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] i915/gvt: seperate tracked MMIO table from
 handlers.c

On Tue, Nov 09, 2021 at 10:51:27AM +0000, Wang, Zhi A wrote:
> Can you elaborate more about this? We need the hash query from the table 
> ASAP when the hypervisor trapped a mmio access. It's a critical path and 
> we tried different data structure in the kernel and the hash table gives 
> the best performance.

Ok, I misunderstood the hashtable.h interface.  hash_for_each_possible
actually does a hash lookup instead of an interation despite the rather
misleading name.