linux-kernel - Re: [RFC 01/19] staging: qlge: fix incorrect truesize accounting

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Message-ID: <YNK+s9Rm7OtL++YM@d3>
Date:   Wed, 23 Jun 2021 13:55:15 +0900
From:   Benjamin Poirier <benjamin.poirier@...il.com>
To:     Coiby Xu <coiby.xu@...il.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        linux-staging@...ts.linux.dev, netdev@...r.kernel.org,
        Shung-Hsi Yu <shung-hsi.yu@...e.com>,
        Manish Chopra <manishc@...vell.com>,
        "supporter:QLOGIC QLGE 10Gb ETHERNET DRIVER" 
        <GR-Linux-NIC-Dev@...vell.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 01/19] staging: qlge: fix incorrect truesize accounting

On 2021-06-22 19:36 +0800, Coiby Xu wrote:
> On Mon, Jun 21, 2021 at 05:10:27PM +0300, Dan Carpenter wrote:
> > On Mon, Jun 21, 2021 at 09:48:44PM +0800, Coiby Xu wrote:
> > > Commit 7c734359d3504c869132166d159c7f0649f0ab34 ("qlge: Size RX buffers
> > > based on MTU") introduced page_chunk structure. We should add
> > > qdev->lbq_buf_size to skb->truesize after __skb_fill_page_desc.
> > > 
> > 
> > Add a Fixes tag.
> 
> I will fix it in next version, thanks!
> 
> > 
> > The runtime impact of this is just that ethtool will report things
> > incorrectly, right?  It's not 100% from the commit message.  Could you
> > please edit the commit message so that an ignoramous like myself can
> > understand it?

truesize is used in socket memory accounting, the stuff behind sysctl
net.core.rmem_max, SO_RCVBUF, ss -m, ...

Some helpful chap wrote a page about it a while ago:
http://vger.kernel.org/~davem/skb_sk.html

> 
> I'm not sure how it would affect ethtool. But according to "git log
> --grep=truesize", it affects coalescing SKBs. Btw, I fixed the issue
> according to the definition of truesize which according to Linux Kernel
> Network by Rami Rosen, it's defined as follows,
> > The total memory allocated for the SKB (including the SKB structure
> > itself and the size of the allocated data block).
> 
> I'll edit the commit message to include it, thanks!
> 
> > 
> > Why is this an RFC instead of just a normal patch which we can apply?
> 
> After doing the tests mentioned in the cover letter, I found Red Hat's
> network QE team has quite a rigorous test suite. But I needed to return the
> machine before having the time to learn about the test suite and run it by
> myself. So I mark it as an RFC before I borrow the machine again to run the
> test suite.

Interesting. Is this test suite based on a public project?