Author: mav
Date: Mon May 4 19:33:51 2015
New Revision: 282427
URL: https://svnweb.freebsd.org/changeset/base/282427
Log:
MFC r281765:
Activate write-only optimization if bpf device opened with O_WRONLY.
dhclient opens bpf as write-only to send packets. It never reads received
packets from that descriptor, but processing them in kernel takes time.
Especially much time takes packet timestamping on systems with expensive
timecounter, such as bhyve guest, where network speed dropped in half.
Sponsored by: iXsystems, Inc.
Modified:
stable/10/sys/net/bpf.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/net/bpf.c
==============================================================================
--- stable/10/sys/net/bpf.c Mon May 4 18:49:25 2015 (r282426)
+++ stable/10/sys/net/bpf.c Mon May 4 19:33:51 2015 (r282427)
@@ -600,7 +600,7 @@ bpf_attachd(struct bpf_d *d, struct bpf_
* Save sysctl value to protect from sysctl change
* between reads
*/
- op_w = V_bpf_optimize_writers;
+ op_w = V_bpf_optimize_writers || d->bd_writer;
if (d->bd_bif != NULL)
bpf_detachd_locked(d);
@@ -802,6 +802,8 @@ bpfopen(struct cdev *dev, int flags, int
* particular buffer method.
*/
bpf_buffer_init(d);
+ if ((flags & FREAD) == 0)
+ d->bd_writer = 2;
d->bd_hbuf_in_use = 0;
d->bd_bufmode = BPF_BUFMODE_BUFFER;
d->bd_sig = SIGIO;
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