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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] compound skb frag pages appearing in start_xmit
Wednesday, October 10, 2012, 12:13:04 PM, you wrote:
> On Tue, 2012-10-09 at 15:40 +0100, Ian Campbell wrote:
>> On Tue, 2012-10-09 at 15:27 +0100, Eric Dumazet wrote:
>> > On Tue, 2012-10-09 at 15:17 +0100, Ian Campbell wrote:
>> >
>> > > Does the higher order pages effectively reduce the number of frags which
>> > > are in use? e.g if MAX_SKB_FRAGS is 16, then for order-0 pages you could
>> > > have 64K worth of frag data.
>> > >
>> > > If we switch to order-3 pages everywhere then can the skb contain 512K
>> > > of data, or does the effective maximum number of frags in an skb reduce
>> > > to 2?
>> >
>> > effective number of frags reduce to 2 or 3
>> >
>> > (We still limit GSO packets to ~63536 bytes)
>>
>> Great! Then I think the fix is more/less trivial...
> The following seems to work for me.
But it doesn't seem to work for me ... dmesg attached.
I don't know if the "mcelog:4359 map pfn expected mapping type write-back for
[mem 0x0009f000-0x000a0fff], got uncached-minus"
is related, is shows up right after the nics get initialized ?
netback still fails with:
[ 191.777994] ------------[ cut here ]------------
[ 191.784245] kernel BUG at drivers/net/xen-netback/netback.c:481!
[ 191.790423] invalid opcode: 0000 [#1] PREEMPT SMP
[ 191.796462] Modules linked in:
[ 191.802315] CPU 1
[ 191.802367] Pid: 1177, comm: netback/1 Tainted: G W
3.6.0pre-rc1-20121010 #1 MSI MS-7640/890FXA-GD70 (MS-7640)
[ 191.814043] RIP: e030:[<ffffffff8146de61>] [<ffffffff8146de61>]
netbk_gop_frag_copy+0x3f1/0x400
[ 191.820171] RSP: e02b:ffff880037c6bb98 EFLAGS: 00010246
[ 191.826271] RAX: 0000000000000244 RBX: ffffc90010827f98 RCX: ffff880031ed9880
[ 191.832450] RDX: 00000000000000a8 RSI: ffff880037c6bd24 RDI: ffffea0000b03f80
[ 191.838581] RBP: ffff880037c6bc28 R08: ffff8800319f8100 R09: 0000000000001000
[ 191.844739] R10: 0000000000000000 R11: 0000000000000132 R12: 00000000000000a8
[ 191.850785] R13: ffff880037c6bcd8 R14: 0000000000001000 R15: ffffc9001082cf70
[ 191.856741] FS: 00007f9f3c944700(0000) GS:ffff88003f840000(0000)
knlGS:0000000000000000
[ 191.862841] CS: e033 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 191.868901] CR2: 0000000001337ca0 CR3: 0000000032cec000 CR4: 0000000000000660
[ 191.875053] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 191.881175] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 191.887247] Process netback/1 (pid: 1177, threadinfo ffff880037c6a000, task
ffff880039984140)
[ 191.893325] Stack:
[ 191.899328] ffff880037c6bd24 00000000000000a8 ffff8800319f8100
ffff880031ed9880
[ 191.905534] ffffc90000000000 0000000000001000 0000000000000000
0000000000000000
[ 191.911742] ffff880000000000 ffffffff817459f3 ffffc90010823420
ffffea0000b03f80
[ 191.917898] Call Trace:
[ 191.923939] [<ffffffff817459f3>] ? _raw_spin_unlock_irqrestore+0x53/0xa0
[ 191.930141] [<ffffffff8146e1cb>] xen_netbk_rx_action+0x30b/0x830
[ 191.936543] [<ffffffff810ad22d>] ? trace_hardirqs_on+0xd/0x10
[ 191.942942] [<ffffffff8146f6da>] xen_netbk_kthread+0xba/0xa90
[ 191.949147] [<ffffffff81095b06>] ? try_to_wake_up+0x1b6/0x310
[ 191.955250] [<ffffffff81086b40>] ? wake_up_bit+0x40/0x40
[ 191.961421] [<ffffffff8146f620>] ? xen_netbk_tx_build_gops+0xa70/0xa70
[ 191.967660] [<ffffffff810864d6>] kthread+0xd6/0xe0
[ 191.973834] [<ffffffff81086400>] ? __init_kthread_worker+0x70/0x70
[ 191.979953] [<ffffffff8174677c>] ret_from_fork+0x7c/0x90
[ 191.986107] [<ffffffff81086400>] ? __init_kthread_worker+0x70/0x70
[ 191.992174] Code: b8 b3 00 00 48 8d 8c f1 60 01 00 00 48 3b 14 01 0f 85 72
fc ff ff e9 7a fc ff ff 0f 0b eb fe 0f 0b eb fe 0f 0b eb fe 0f 0b eb fe <0f> 0b
eb fe 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 48 83
[ 192.005230] RIP [<ffffffff8146de61>] netbk_gop_frag_copy+0x3f1/0x400
[ 192.011786] RSP <ffff880037c6bb98>
[ 192.018402] ---[ end trace c51ab5e2c2c918fc ]---
--
Sander
> I haven't tackled netfront yet.
> 8<--------------------------------------------------------------
> From 551e42e3dd203f2eb97cb082985013bb33b8f020 Mon Sep 17 00:00:00 2001
> From: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Date: Tue, 9 Oct 2012 15:51:20 +0100
> Subject: [PATCH] xen: netback: handle compound page fragments on transmit.
> An SKB paged fragment can consist of a compound page with order > 0.
> However the netchannel protocol deals only in PAGE_SIZE frames.
> Handle this in netbk_gop_frag_copy and xen_netbk_count_skb_slots by
> iterating over the frames which make up the page.
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>
> Cc: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
> ---
> drivers/net/xen-netback/netback.c | 40 ++++++++++++++++++++++++++++++++----
> 1 files changed, 35 insertions(+), 5 deletions(-)
> diff --git a/drivers/net/xen-netback/netback.c
> b/drivers/net/xen-netback/netback.c
> index 4ebfcf3..d747e30 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -335,21 +335,35 @@ unsigned int xen_netbk_count_skb_slots(struct xenvif
> *vif, struct sk_buff *skb)
>
> for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
> unsigned long size =
> skb_frag_size(&skb_shinfo(skb)->frags[i]);
> + unsigned long offset = skb_shinfo(skb)->frags[i].page_offset;
> unsigned long bytes;
> +
> + offset &= ~PAGE_MASK;
> +
> while (size > 0) {
> + BUG_ON(offset >= PAGE_SIZE);
> BUG_ON(copy_off > MAX_BUFFER_OFFSET);
>
> - if (start_new_rx_buffer(copy_off, size, 0)) {
> + bytes = PAGE_SIZE - offset;
> +
> + if (bytes > size)
> + bytes = size;
> +
> + if (start_new_rx_buffer(copy_off, bytes, 0)) {
> count++;
> copy_off = 0;
> }
>
> - bytes = size;
> if (copy_off + bytes > MAX_BUFFER_OFFSET)
> bytes = MAX_BUFFER_OFFSET - copy_off;
>
> copy_off += bytes;
> +
> + offset += bytes;
> size -= bytes;
> +
> + if (offset == PAGE_SIZE)
> + offset = 0;
> }
> }
> return count;
> @@ -403,14 +417,24 @@ static void netbk_gop_frag_copy(struct xenvif *vif,
> struct sk_buff *skb,
> unsigned long bytes;
>
> /* Data must not cross a page boundary. */
> - BUG_ON(size + offset > PAGE_SIZE);
> + BUG_ON(size + offset > PAGE_SIZE<<compound_order(page));
>
> meta = npo->meta + npo->meta_prod - 1;
>
> + /* Skip unused frames from start of page */
> + page += offset >> PAGE_SHIFT;
> + offset &= ~PAGE_MASK;
> +
> while (size > 0) {
> + BUG_ON(offset >= PAGE_SIZE);
> BUG_ON(npo->copy_off > MAX_BUFFER_OFFSET);
>
> - if (start_new_rx_buffer(npo->copy_off, size, *head)) {
> + bytes = PAGE_SIZE - offset;
> +
> + if (bytes > size)
> + bytes = size;
> +
> + if (start_new_rx_buffer(npo->copy_off, bytes, *head)) {
> /*
> * Netfront requires there to be some data in the head
> * buffer.
> @@ -420,7 +444,6 @@ static void netbk_gop_frag_copy(struct xenvif *vif,
> struct sk_buff *skb,
> meta = get_next_rx_buffer(vif, npo);
> }
>
> - bytes = size;
> if (npo->copy_off + bytes > MAX_BUFFER_OFFSET)
> bytes = MAX_BUFFER_OFFSET - npo->copy_off;
>
> @@ -453,6 +476,13 @@ static void netbk_gop_frag_copy(struct xenvif *vif,
> struct sk_buff *skb,
> offset += bytes;
> size -= bytes;
>
> + /* Next frame */
> + if (offset == PAGE_SIZE) {
> + BUG_ON(!PageCompound(page));
> + page++;
> + offset = 0;
> + }
> +
> /* Leave a gap for the GSO descriptor. */
> if (*head && skb_shinfo(skb)->gso_size && !vif->gso_prefix)
> vif->rx.req_cons++;
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