linux-kernel - Re: [EXT] [PATCH 1/2] net: qed*: Reduce RX and TX default ring count when running inside kdump kernel

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Date:   Wed, 6 May 2020 12:43:03 +0530
From:   Bhupesh Sharma <bhsharma@...hat.com>
To:     Igor Russkikh <irusskikh@...vell.com>
Cc:     netdev@...r.kernel.org, Bhupesh SHARMA <bhupesh.linux@...il.com>,
        kexec mailing list <kexec@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ariel Elior <aelior@...vell.com>,
        GR-everest-linux-l2 <GR-everest-linux-l2@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        "David S . Miller" <davem@...emloft.net>,
        Alok Prasad <palok@...vell.com>
Subject: Re: [EXT] [PATCH 1/2] net: qed*: Reduce RX and TX default ring count
 when running inside kdump kernel

Hello Igor,

On Wed, May 6, 2020 at 12:21 PM Igor Russkikh <irusskikh@...vell.com> wrote:
>
>
>
> >  #include <linux/compiler.h>
> > +#include <linux/crash_dump.h>
> >  #include <linux/version.h>
> >  #include <linux/workqueue.h>
> >  #include <linux/netdevice.h>
> > @@ -574,13 +575,13 @@ int qede_add_tc_flower_fltr(struct qede_dev *edev,
> > __be16 proto,
> >  #define RX_RING_SIZE         ((u16)BIT(RX_RING_SIZE_POW))
> >  #define NUM_RX_BDS_MAX               (RX_RING_SIZE - 1)
> >  #define NUM_RX_BDS_MIN               128
> > -#define NUM_RX_BDS_DEF               ((u16)BIT(10) - 1)
> > +#define NUM_RX_BDS_DEF               ((is_kdump_kernel()) ? ((u16)BIT(6) - 1) :
> > ((u16)BIT(10) - 1))
> >
> >  #define TX_RING_SIZE_POW     13
> >  #define TX_RING_SIZE         ((u16)BIT(TX_RING_SIZE_POW))
> >  #define NUM_TX_BDS_MAX               (TX_RING_SIZE - 1)
> >  #define NUM_TX_BDS_MIN               128
> > -#define NUM_TX_BDS_DEF               NUM_TX_BDS_MAX
> > +#define NUM_TX_BDS_DEF               ((is_kdump_kernel()) ? ((u16)BIT(6) - 1) :
> > NUM_TX_BDS_MAX)
> >
>
> Hi Bhupesh,
>
> Thanks for looking into this. We are also analyzing how to reduce qed* memory
> usage even more.
>
> Patch is good, but may I suggest not to introduce conditional logic into the
> defines but instead just add two new defines like NUM_[RT]X_BDS_MIN and check
> for is_kdump_kernel() in the code explicitly?
>
> if (is_kdump_kernel()) {
>         edev->q_num_rx_buffers = NUM_RX_BDS_MIN;
>         edev->q_num_tx_buffers = NUM_TX_BDS_MIN;
> } else {
>         edev->q_num_rx_buffers = NUM_RX_BDS_DEF;
>         edev->q_num_tx_buffers = NUM_TX_BDS_DEF;
> }
>
> This may make configuration logic more explicit. If future we may want adding
> more specific configs under this `if`.

Thanks for the review comments.
The suggestions seem fine to me. I will incorporate them in v2.

Regards,
Bhupesh