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Re: [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to VQs |
Date: |
Wed, 16 Dec 2015 09:38:36 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 |
On 15/12/2015 23:33, Vincenzo Maffione wrote:
> This patch slightly rewrites the code to reduce the number of accesses, since
> many of them seems unnecessary to me. After this reduction, the bottleneck
> jumps from 1 Mpps to 2 Mpps.
Very nice. Did you get new numbers with the rebase? That would help
measuring the effect of removing variable-sized memcpy (I'll post the
patches for this shortly; they're entirely in memory.h/exec.c so they're
not virtio-specific). A rough measurement from "perf" says they're
worth about 5%.
Related to this, patch 3 introduces a variable-sized memcpy, because it
switches from 2 virtio_stl_phys to 1 address_space_write. I'm curious
if the effect of this individual patch is positive, negative or neutral.
On the other hand, patches 1 and 2 are clear wins.
Paolo
> Patch is not complete (e.g. it still does not properly manage endianess, it is
> not clean, etc.). I just wanted to ask if you think the idea makes sense, and
> a proper patch in this direction would be accepted.
- [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to VQs, Vincenzo Maffione, 2015/12/15
- [Qemu-devel] [PATCH v2 3/3] virtio: combine write of an entry into used ring, Vincenzo Maffione, 2015/12/15
- [Qemu-devel] [PATCH v2 2/3] virtio: read avail_idx from VQ only when necessary, Vincenzo Maffione, 2015/12/15
- [Qemu-devel] [PATCH v2 1/3] virtio: cache used_idx in a VirtQueue field, Vincenzo Maffione, 2015/12/15
- Re: [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to VQs,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to VQs, Vincenzo Maffione, 2015/12/16
- Re: [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to VQs, Paolo Bonzini, 2015/12/16
- Re: [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to VQs, Vincenzo Maffione, 2015/12/16
- Re: [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to VQs, Paolo Bonzini, 2015/12/16
- Re: [Qemu-devel] [PATCH v2 0/3] virtio: proposal to optimize accesses to VQs, Vincenzo Maffione, 2015/12/30