linux-kernel - Re: [RFC PATCH] xhci: Use Cached ring during endpoint ring allocation

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Date:   Thu, 23 Feb 2017 18:15:01 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>,
        mathias.nyman@...el.com, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        anirudh@...inx.com, punnaia@...inx.com,
        Anurag Kumar Vulisha <anuragku@...inx.com>
Subject: Re: [RFC PATCH] xhci: Use Cached ring during endpoint ring allocation

On 22.02.2017 17:05, Anurag Kumar Vulisha wrote:
> Currently during endpoint initialization, a new endpoint ring is alloacte
> using xhci_ring_alloc(), if this function fails to allocate ring a cached
> ring(if available) is assigned to endpoint ring.
> This patch modifies the code that during endpoint initialization, if cached
> ring is available it is assigned to the endpoint ring. If cached rings are
> not available then xhci_ring_alloc() is called to allocate a new ring.
> Doing so will avoid unncessary memory allocations if cached ring is already
> available for use. This also fixes endpoint "Ring expansion failed" error
> which occurs due to insufficient memory during ring expansion.
>
> Signed-off-by: Anurag Kumar Vulisha <anuragku@...inx.com>

Thanks for bringing this to my attention.
Your approach certainly makes more sense than the current way.

I need to check history why this type of ring cache was created in the first place.
It's possible that the whole ring cache is not really useful anymore

-Mathias