From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Miller <davem@davemloft.net>
Cc: anant.thazhemadam@gmail.com, jasowang@redhat.com,
kuba@kernel.org, ast@kernel.org, daniel@iogearbox.net,
hawk@kernel.org, john.fastabend@gmail.com,
linux-kernel-mentees@lists.linuxfoundation.org,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org
Subject: Re: [Linux-kernel-mentees][PATCH 0/2] reorder members of structures in virtio_net for optimization
Date: Sat, 3 Oct 2020 14:43:13 -0400 [thread overview]
Message-ID: <20201003144300-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20201002.190638.1090456279017490485.davem@davemloft.net>
On Fri, Oct 02, 2020 at 07:06:38PM -0700, David Miller wrote:
> From: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> Date: Wed, 30 Sep 2020 10:47:20 +0530
>
> > The structures virtnet_info and receive_queue have byte holes in
> > middle, and their members could do with some rearranging
> > (order-of-declaration wise) in order to overcome this.
> >
> > Rearranging the members helps in:
> > * elimination the byte holes in the middle of the structures
> > * reduce the size of the structure (virtnet_info)
> > * have more members stored in one cache line (as opposed to
> > unnecessarily crossing the cacheline boundary and spanning
> > different cachelines)
> >
> > The analysis was performed using pahole.
> >
> > These patches may be applied in any order.
>
> What effects do these changes have on performance?
>
> The cache locality for various TX and RX paths could be effected.
>
> I'm not applying these patches without some data on the performance
> impact.
>
> Thank you.
Agree wholeheartedly.
--
MST
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Miller <davem@davemloft.net>
Cc: anant.thazhemadam@gmail.com, hawk@kernel.org,
daniel@iogearbox.net, netdev@vger.kernel.org,
jasowang@redhat.com, john.fastabend@gmail.com, ast@kernel.org,
virtualization@lists.linux-foundation.org, kuba@kernel.org,
bpf@vger.kernel.org,
linux-kernel-mentees@lists.linuxfoundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [Linux-kernel-mentees] [PATCH 0/2] reorder members of structures in virtio_net for optimization
Date: Sat, 3 Oct 2020 14:43:13 -0400 [thread overview]
Message-ID: <20201003144300-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20201002.190638.1090456279017490485.davem@davemloft.net>
On Fri, Oct 02, 2020 at 07:06:38PM -0700, David Miller wrote:
> From: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> Date: Wed, 30 Sep 2020 10:47:20 +0530
>
> > The structures virtnet_info and receive_queue have byte holes in
> > middle, and their members could do with some rearranging
> > (order-of-declaration wise) in order to overcome this.
> >
> > Rearranging the members helps in:
> > * elimination the byte holes in the middle of the structures
> > * reduce the size of the structure (virtnet_info)
> > * have more members stored in one cache line (as opposed to
> > unnecessarily crossing the cacheline boundary and spanning
> > different cachelines)
> >
> > The analysis was performed using pahole.
> >
> > These patches may be applied in any order.
>
> What effects do these changes have on performance?
>
> The cache locality for various TX and RX paths could be effected.
>
> I'm not applying these patches without some data on the performance
> impact.
>
> Thank you.
Agree wholeheartedly.
--
MST
_______________________________________________
Linux-kernel-mentees mailing list
Linux-kernel-mentees@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees
WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: David Miller <davem@davemloft.net>
Cc: anant.thazhemadam@gmail.com, hawk@kernel.org,
daniel@iogearbox.net, netdev@vger.kernel.org,
john.fastabend@gmail.com, ast@kernel.org,
virtualization@lists.linux-foundation.org, kuba@kernel.org,
bpf@vger.kernel.org,
linux-kernel-mentees@lists.linuxfoundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [Linux-kernel-mentees][PATCH 0/2] reorder members of structures in virtio_net for optimization
Date: Sat, 3 Oct 2020 14:43:13 -0400 [thread overview]
Message-ID: <20201003144300-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20201002.190638.1090456279017490485.davem@davemloft.net>
On Fri, Oct 02, 2020 at 07:06:38PM -0700, David Miller wrote:
> From: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> Date: Wed, 30 Sep 2020 10:47:20 +0530
>
> > The structures virtnet_info and receive_queue have byte holes in
> > middle, and their members could do with some rearranging
> > (order-of-declaration wise) in order to overcome this.
> >
> > Rearranging the members helps in:
> > * elimination the byte holes in the middle of the structures
> > * reduce the size of the structure (virtnet_info)
> > * have more members stored in one cache line (as opposed to
> > unnecessarily crossing the cacheline boundary and spanning
> > different cachelines)
> >
> > The analysis was performed using pahole.
> >
> > These patches may be applied in any order.
>
> What effects do these changes have on performance?
>
> The cache locality for various TX and RX paths could be effected.
>
> I'm not applying these patches without some data on the performance
> impact.
>
> Thank you.
Agree wholeheartedly.
--
MST
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2020-10-03 18:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-30 5:17 [Linux-kernel-mentees][PATCH 0/2] reorder members of structures in virtio_net for optimization Anant Thazhemadam
2020-09-30 5:17 ` [Linux-kernel-mentees] [PATCH " Anant Thazhemadam
2020-09-30 5:17 ` [Linux-kernel-mentees][PATCH 1/2] net: reorder members of virtnet_info " Anant Thazhemadam
2020-09-30 5:17 ` [Linux-kernel-mentees] [PATCH " Anant Thazhemadam
2020-09-30 5:17 ` [Linux-kernel-mentees][PATCH 2/2] net: reorder members of receive_queue in virtio_net " Anant Thazhemadam
2020-09-30 5:17 ` [Linux-kernel-mentees] [PATCH " Anant Thazhemadam
2020-10-03 2:06 ` [Linux-kernel-mentees][PATCH 0/2] reorder members of structures " David Miller
2020-10-03 2:06 ` David Miller
2020-10-03 2:06 ` [Linux-kernel-mentees] [PATCH " David Miller
2020-10-03 18:43 ` Michael S. Tsirkin [this message]
2020-10-03 18:43 ` [Linux-kernel-mentees][PATCH " Michael S. Tsirkin
2020-10-03 18:43 ` [Linux-kernel-mentees] [PATCH " Michael S. Tsirkin
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