From: "Yuan, Linyu (NSB - CN/Shanghai)" <linyu.yuan@nokia-sbell.com>
To: Madalin-cristian Bucur <madalin.bucur@nxp.com>,
yuan linyu <cugyly@163.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: "David S . Miller" <davem@davemloft.net>
Subject: RE: [PATCH net-next] net: dpaa: remove init which already done in per-cpu allocation
Date: Mon, 30 Oct 2017 06:15:53 +0000 [thread overview]
Message-ID: <3c448bbf3ebb4de0843b78af23435ba0@nokia-sbell.com> (raw)
In-Reply-To: <DB3PR0402MB384999DB4601EA7BE1E9159FEC590@DB3PR0402MB3849.eurprd04.prod.outlook.com>
I just saw below accepted commit, it said "per cpu allocations are already zeroed, no need to clear them again."
https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=bfd8e5a407133e58a92a38ccf3d0ba6db81f22d8
I will not touch memory sub-system, so I will not change this function description.
> -----Original Message-----
> From: Madalin-cristian Bucur [mailto:madalin.bucur@nxp.com]
> Sent: Monday, October 30, 2017 1:56 PM
> To: Yuan, Linyu (NSB - CN/Shanghai); yuan linyu; netdev@vger.kernel.org;
> gregkh@linuxfoundation.org
> Cc: David S . Miller
> Subject: RE: [PATCH net-next] net: dpaa: remove init which already done in
> per-cpu allocation
>
> Also here:
>
> http://elixir.free-electrons.com/linux/latest/source/mm/percpu.c#L717
>
> Should the fact that the memory is zeroed be included in the function
> description?
>
> /**
> * pcpu_alloc - the percpu allocator
> * @size: size of area to allocate in bytes
> * @align: alignment of area (max PAGE_SIZE)
> * @reserved: allocate from the reserved chunk if available
> * @gfp: allocation flags
> *
> * Allocate percpu area of @size bytes aligned at @align. If @gfp doesn't
> * contain %GFP_KERNEL, the allocation is atomic.
> *
> * RETURNS:
> * Percpu pointer to the allocated area on success, NULL on failure.
> */
>
> Now it seems to be an implementation detail rather than a guarantee.
>
> Looking at Documentation/driver-model/devres.txt, the memset is not
> mentioned there either.
>
> > -----Original Message-----
> > From: Yuan, Linyu (NSB - CN/Shanghai) [mailto:linyu.yuan@nokia-sbell.com]
> > Sent: Monday, October 30, 2017 7:21 AM
> > To: Madalin-cristian Bucur <madalin.bucur@nxp.com>; yuan linyu
> > <cugyly@163.com>; netdev@vger.kernel.org
> > Cc: David S . Miller <davem@davemloft.net>
> > Subject: RE: [PATCH net-next] net: dpaa: remove init which already done in
> > per-cpu allocation
> >
> > http://elixir.free-electrons.com/linux/latest/source/mm/percpu.c#L1018
> >
> > > -----Original Message-----
> > > From: Madalin-cristian Bucur [mailto:madalin.bucur@nxp.com]
> > > Sent: Monday, October 30, 2017 1:15 PM
> > > To: Yuan, Linyu (NSB - CN/Shanghai); yuan linyu; netdev@vger.kernel.org
> > > Cc: David S . Miller
> > > Subject: RE: [PATCH net-next] net: dpaa: remove init which already done
> > in
> > > per-cpu allocation
> > >
> > > Is the memset part documented?
> > > Can you point to the specific comment & code that does it?
> > >
> > > Thanks
> > >
> > > > -----Original Message-----
> > > > From: Yuan, Linyu (NSB - CN/Shanghai) [mailto:linyu.yuan@nokia-
> > sbell.com]
> > > > Sent: Monday, October 30, 2017 7:12 AM
> > > > To: Madalin-cristian Bucur <madalin.bucur@nxp.com>; yuan linyu
> > > > <cugyly@163.com>; netdev@vger.kernel.org
> > > > Cc: David S . Miller <davem@davemloft.net>
> > > > Subject: RE: [PATCH net-next] net: dpaa: remove init which already
> > done in
> > > > per-cpu allocation
> > > >
> > > > Hi,
> > > >
> > > > devm_alloc_percpu() will allocate per-cpu memory and memset allocated
> > > > block content to 0.
> > > >
> > > > > -----Original Message-----
> > > > > From: Madalin-cristian Bucur [mailto:madalin.bucur@nxp.com]
> > > > > Sent: Monday, October 30, 2017 1:08 PM
> > > > > To: yuan linyu; netdev@vger.kernel.org
> > > > > Cc: David S . Miller; Yuan, Linyu (NSB - CN/Shanghai)
> > > > > Subject: RE: [PATCH net-next] net: dpaa: remove init which already
> > done
> > > > in
> > > > > per-cpu allocation
> > > > >
> > > > > Hi Yuan,
> > > > >
> > > > > Can you please give more details about this change you are
> > proposing?
> > > > >
> > > > > Regards,
> > > > > Madalin
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: netdev-owner@vger.kernel.org
> > > > > [mailto:netdev-owner@vger.kernel.org]
> > > > > > On Behalf Of yuan linyu
> > > > > > Sent: Sunday, October 29, 2017 3:49 AM
> > > > > > To: netdev@vger.kernel.org
> > > > > > Cc: David S . Miller <davem@davemloft.net>; yuan linyu
> > > > > > <Linyu.Yuan@alcatel-sbell.com.cn>
> > > > > > Subject: [PATCH net-next] net: dpaa: remove init which already
> > done in
> > > > > > per-cpu allocation
> > > > > >
> > > > > > From: yuan linyu <Linyu.Yuan@alcatel-sbell.com.cn>
> > > > > >
> > > > > > Signed-off-by: yuan linyu <Linyu.Yuan@alcatel-sbell.com.cn>
> > > > > > ---
> > > > > > drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 4 ----
> > > > > > 1 file changed, 4 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > > > b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > > > index a8d0be8..1ccc316 100644
> > > > > > --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > > > +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > > > > > @@ -2814,10 +2814,6 @@ static int dpaa_eth_probe(struct
> > > > > platform_device
> > > > > > *pdev)
> > > > > > err = -ENOMEM;
> > > > > > goto free_dpaa_fqs;
> > > > > > }
> > > > > > - for_each_possible_cpu(i) {
> > > > > > - percpu_priv = per_cpu_ptr(priv->percpu_priv, i);
> > > > > > - memset(percpu_priv, 0, sizeof(*percpu_priv));
> > > > > > - }
> > > > > >
> > > > > > priv->num_tc = 1;
> > > > > > netif_set_real_num_tx_queues(net_dev, priv->num_tc *
> > > > > > DPAA_TC_TXQ_NUM);
> > > > > > --
> > > > > > 2.7.4
> > > > > >
next prev parent reply other threads:[~2017-10-30 6:15 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-29 1:48 [PATCH net-next] net: dpaa: remove init which already done in per-cpu allocation yuan linyu
2017-10-30 5:08 ` Madalin-cristian Bucur
2017-10-30 5:12 ` Yuan, Linyu (NSB - CN/Shanghai)
2017-10-30 5:15 ` Madalin-cristian Bucur
2017-10-30 5:20 ` Yuan, Linyu (NSB - CN/Shanghai)
2017-10-30 5:56 ` Madalin-cristian Bucur
2017-10-30 6:15 ` Yuan, Linyu (NSB - CN/Shanghai) [this message]
2017-10-30 7:13 ` Madalin-cristian Bucur
2017-10-30 7:17 ` Madalin-cristian Bucur
2017-11-01 3:09 ` David Miller
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