From: Paolo Bonzini <pbonzini@redhat.com>
To: unlisted-recipients:; (no To-header on input)
Cc: Rusty Russell <rusty@rustcorp.com.au>,
kvm@vger.kernel.org, mst@redhat.com,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 0/9] virtio: new API for addition of buffers, scatterlist changes
Date: Fri, 15 Feb 2013 19:04:19 +0100 [thread overview]
Message-ID: <511E78A3.9070607@redhat.com> (raw)
In-Reply-To: <511CAD19.2010902@redhat.com>
Il 14/02/2013 10:23, Paolo Bonzini ha scritto:
>> > How about this as a first step?
>> >
>> > virtio_ring: virtqueue_add_sgs, to add multiple sgs.
>> >
>> > virtio_scsi and virtio_blk can really use these, to avoid their current
>> > hack of copying the whole sg array.
>> >
>> > Signed-off-by: Ruty Russell <rusty@rustcorp.com.au>
> It's much better than the other prototype you had posted, but I still
> dislike this... You pay for additional counting of scatterlists when
> the caller knows the number of buffers; and the nested loops aren't
> free, either.
Another problem is that you cannot pass "truncated" scatterlists. You
must ensure there is an end marker on the last item. I'm not sure if
the kernel ensures that, given that for_each_sg takes explicitly the
number of scatterlist elements; and it is not as trivial as
"sg_mark_end(foo + nsg - 1);" if the upper layers hand you a chained
scatterlist.
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
Cc: virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
mst@redhat.com
Subject: Re: [PATCH 0/9] virtio: new API for addition of buffers, scatterlist changes
Date: Fri, 15 Feb 2013 19:04:19 +0100 [thread overview]
Message-ID: <511E78A3.9070607@redhat.com> (raw)
In-Reply-To: <511CAD19.2010902@redhat.com>
Il 14/02/2013 10:23, Paolo Bonzini ha scritto:
>> > How about this as a first step?
>> >
>> > virtio_ring: virtqueue_add_sgs, to add multiple sgs.
>> >
>> > virtio_scsi and virtio_blk can really use these, to avoid their current
>> > hack of copying the whole sg array.
>> >
>> > Signed-off-by: Ruty Russell <rusty@rustcorp.com.au>
> It's much better than the other prototype you had posted, but I still
> dislike this... You pay for additional counting of scatterlists when
> the caller knows the number of buffers; and the nested loops aren't
> free, either.
Another problem is that you cannot pass "truncated" scatterlists. You
must ensure there is an end marker on the last item. I'm not sure if
the kernel ensures that, given that for_each_sg takes explicitly the
number of scatterlist elements; and it is not as trivial as
"sg_mark_end(foo + nsg - 1);" if the upper layers hand you a chained
scatterlist.
Paolo
next prev parent reply other threads:[~2013-02-15 18:04 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-12 12:23 [PATCH 0/9] virtio: new API for addition of buffers, scatterlist changes Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-12 12:23 ` [PATCH 1/9] virtio: add functions for piecewise addition of buffers Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-12 14:56 ` Michael S. Tsirkin
2013-02-12 14:56 ` Michael S. Tsirkin
2013-02-12 15:32 ` Paolo Bonzini
2013-02-12 15:32 ` Paolo Bonzini
2013-02-12 15:43 ` Michael S. Tsirkin
2013-02-12 15:43 ` Michael S. Tsirkin
2013-02-12 15:48 ` Paolo Bonzini
2013-02-12 15:48 ` Paolo Bonzini
2013-02-12 16:13 ` Michael S. Tsirkin
2013-02-12 16:13 ` Michael S. Tsirkin
2013-02-12 16:17 ` Paolo Bonzini
2013-02-12 16:17 ` Paolo Bonzini
2013-02-12 16:35 ` Michael S. Tsirkin
2013-02-12 16:35 ` Michael S. Tsirkin
2013-02-12 16:57 ` Paolo Bonzini
2013-02-12 16:57 ` Paolo Bonzini
2013-02-12 17:34 ` Michael S. Tsirkin
2013-02-12 17:34 ` Michael S. Tsirkin
2013-02-12 18:04 ` Paolo Bonzini
2013-02-12 18:04 ` Paolo Bonzini
2013-02-12 18:23 ` Michael S. Tsirkin
2013-02-12 18:23 ` Michael S. Tsirkin
2013-02-12 20:08 ` Paolo Bonzini
2013-02-12 20:08 ` Paolo Bonzini
2013-02-12 20:49 ` Michael S. Tsirkin
2013-02-12 20:49 ` Michael S. Tsirkin
2013-02-13 8:06 ` Paolo Bonzini
2013-02-13 10:33 ` Michael S. Tsirkin
2013-02-12 18:03 ` [PATCH v2 " Paolo Bonzini
2013-02-12 18:03 ` Paolo Bonzini
2013-02-12 12:23 ` [PATCH 2/9] virtio-blk: reorganize virtblk_add_req Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-17 6:38 ` Asias He
2013-02-17 6:38 ` Asias He
2013-02-12 12:23 ` [PATCH 3/9] virtio-blk: use virtqueue_start_buf on bio path Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-17 6:39 ` Asias He
2013-02-17 6:39 ` Asias He
2013-02-12 12:23 ` [PATCH 4/9] virtio-blk: use virtqueue_start_buf on req path Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-17 6:37 ` Asias He
2013-02-17 6:37 ` Asias He
2013-02-18 9:05 ` Paolo Bonzini
2013-02-18 9:05 ` Paolo Bonzini
2013-02-12 12:23 ` [PATCH 5/9] scatterlist: introduce sg_unmark_end Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-12 12:23 ` [PATCH 6/9] virtio-net: unmark scatterlist ending after virtqueue_add_buf Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-12 12:23 ` [PATCH 7/9] virtio-scsi: use virtqueue_start_buf Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-12 12:23 ` [PATCH 8/9] virtio: introduce and use virtqueue_add_buf_single Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-12 12:23 ` [PATCH 9/9] virtio: reimplement virtqueue_add_buf using new functions Paolo Bonzini
2013-02-12 12:23 ` Paolo Bonzini
2013-02-14 6:00 ` [PATCH 0/9] virtio: new API for addition of buffers, scatterlist changes Rusty Russell
2013-02-14 6:00 ` Rusty Russell
2013-02-14 9:23 ` Paolo Bonzini
2013-02-14 9:23 ` Paolo Bonzini
2013-02-15 18:04 ` Paolo Bonzini [this message]
2013-02-15 18:04 ` Paolo Bonzini
2013-02-19 7:49 ` Rusty Russell
2013-02-19 7:49 ` Rusty Russell
2013-02-19 9:11 ` Paolo Bonzini
2013-02-19 9:11 ` Paolo Bonzini
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