On 2/12/19 6:58 PM, Eric Dumazet wrote:
> In the past, we tried to increase the buffer size up to 32 KB in order
> to reduce number of syscalls per dump.
>
> Commit 2d34851cd341 ("lib/libnetlink: re malloc buff if size is not enough")
> brought the size back to 4KB because the kernel can not know the application
> is ready to receive bigger requests.
>
> See kernel commits 9063e21fb026 ("netlink: autosize skb lengthes") and
> d35c99ff77ec ("netlink: do not enter direct reclaim from netlink_dump()")
> for more details.
>
> Fixes: 2d34851cd341 ("lib/libnetlink: re malloc buff if size is not enough")
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Cc: Hangbin Liu <liuhang...@gmail.com>
> Cc: Phil Sutter <p...@nwl.cc>
> ---
> lib/libnetlink.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index
> 1892a02ab5d0d73776c9882ffc77edcd2c663d01..0d48a3d43cf03065dacbd419578ab10af56431a4
> 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -718,6 +718,8 @@ static int rtnl_recvmsg(int fd, struct msghdr *msg, char
> **answer)
> if (len < 0)
> return len;
>
> + if (len < 32768)
> + len = 32768;
> buf = malloc(len);
> if (!buf) {
> fprintf(stderr, "malloc error: not enough buffer\n");
>
I believe that negates the whole point of 2d34851cd341 - which I have no
problem with. 2 recvmsg calls per message is overkill.
Do we know of any single message sizes > 32k? 2d34851cd341 cites
increasing VF's but at some point there is a limit. If not, the whole
PEEK thing should go away and we just malloc 32k (or 64k) buffers for
each recvmsg.
