linux-kernel - Re: [PATCH v4 1/2] USB: core: add a memory pool to urb caching host-controller private data

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Message-ID: <2025052257-expectant-macarena-69ee@gregkh>
Date: Thu, 22 May 2025 10:33:42 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: David Wang <00107082@....com>
Cc: mathias.nyman@...el.com, oneukum@...e.com, stern@...land.harvard.edu,
	hminas@...opsys.com, rui.silva@...aro.org, jgross@...e.com,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] USB: core: add a memory pool to urb caching
 host-controller private data

On Thu, May 22, 2025 at 03:09:43PM +0800, David Wang wrote:
> From an end-user's perspective, the performance difference with this change
> is insignificant when system is under no memory pressure, and when under
> heavy memory pressure. When system is under heavy memory pressure,
> everything is slow.  There could be a point in-between no memory pressure
> and heavy memory pressure where these 1k+/s memory allocations would
> dominate the performance, but very hard to pinpoint it.

For this reason alone I can't take this change, sorry.

Also, as others have stated, this could be done in the hcd drivers
themselves if they want to, no need to push this into the usb core.

thanks,

greg k-h