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Re: [Qemu-devel] [PATCH v5] net: Allocating Large sized arrays to heap
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v5] net: Allocating Large sized arrays to heap |
Date: |
Thu, 31 Mar 2016 10:58:49 +0100 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Mon, Mar 28, 2016 at 06:04:11PM +0530, Pooja Dhannawat wrote:
> nc_sendv_compat has a huge stack usage of 69680 bytes approx.
> Moving large arrays to heap to reduce stack usage.
>
> Reviewed-by: Stefan Hajnoczi <address@hidden>
> Signed-off-by: Pooja Dhannawat <address@hidden>
> ---
> net/net.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/net/net.c b/net/net.c
> index b0c832e..663da13 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -709,23 +709,28 @@ ssize_t qemu_send_packet_raw(NetClientState *nc, const
> uint8_t *buf, int size)
> static ssize_t nc_sendv_compat(NetClientState *nc, const struct iovec *iov,
> int iovcnt, unsigned flags)
> {
> - uint8_t buf[NET_BUFSIZE];
> + uint8_t *buf = NULL;
> uint8_t *buffer;
> size_t offset;
> + ssize_t ret;
>
> if (iovcnt == 1) {
> buffer = iov[0].iov_base;
> offset = iov[0].iov_len;
> } else {
> + buf = g_new(uint8_t, NET_BUFSIZE);
> buffer = buf;
> - offset = iov_to_buf(iov, iovcnt, 0, buf, sizeof(buf));
> + offset = iov_to_buf(iov, iovcnt, 0, buf, NET_BUFSIZE);
> }
>
> if (flags & QEMU_NET_PACKET_FLAG_RAW && nc->info->receive_raw) {
> - return nc->info->receive_raw(nc, buffer, offset);
> + ret = nc->info->receive_raw(nc, buffer, offset);
> } else {
> - return nc->info->receive(nc, buffer, offset);
> + ret = nc->info->receive(nc, buffer, offset);
> }
> +
> + g_free(buf);
> + return ret;
> }
>
> ssize_t qemu_deliver_packet_iov(NetClientState *sender,
> --
> 2.5.0
CCing Jason Wang, net subsystem maintainer. Please use
scripts/get_maintainer.pl to find the right people to CC in future
patches.
We may also want to keep a smaller stack buffer so that reasonably-sized
packets (e.g. up to 2 KB) can be send without the performance cost of
g_malloc().
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