4b29d585cf
tree used it incorrectly, which lead to inaccurate overrated
if_obytes accounting. The drbr(9) used to update ifnet stats on
drbr_enqueue(), which is not accurate since enqueuing doesn't
imply successful processing by driver. Dequeuing neither mean
that. Most drivers also called drbr_stats_update() which did
accounting again, leading to doubled if_obytes statistics. And
in case of severe transmitting, when a packet could be several
times enqueued and dequeued it could have been accounted several
times.
o Thus, make drbr(9) API thinner. Now drbr(9) merely chooses between
ALTQ queueing or buf_ring(9) queueing.
- It doesn't touch the buf_ring stats any more.
- It doesn't touch ifnet stats anymore.
- drbr_stats_update() no longer exists.
o buf_ring(9) handles its stats itself:
- It handles br_drops itself.
- br_prod_bytes stats are dropped. Rationale: no one ever
reads them but update of a common counter on every packet
negatively affects performance due to excessive cache
invalidation.
- buf_ring_enqueue_bytes() reduced to buf_ring_enqueue(), since
we no longer account bytes.
o Drivers handle their stats theirselves: if_obytes, if_omcasts.
o mlx4(4), igb(4), em(4), vxge(4), oce(4) and ixv(4) no longer
use drbr_stats_update(), and update ifnet stats theirselves.
o bxe(4) was the most correct driver, it didn't call
drbr_stats_update(), thus it was the only driver accurate under
moderate load. Now it also maintains stats itself.
o ixgbe(4) had already taken stats from hardware, so just
- drop software stats updating.
- take multicast packet count from hardware as well.
o mxge(4) just no longer needs NO_SLOW_STATS define.
o cxgb(4), cxgbe(4) need no change, since they obtain stats
from hardware.
Reviewed by: jfv, gnn
134 lines
3.7 KiB
Groff
134 lines
3.7 KiB
Groff
.\" Copyright (c) 2009 Bitgravity Inc
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.\" Written by: Kip Macy <kmacy@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 27, 2012
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.Dt BUF_RING 9
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.Os
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.Sh NAME
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.Nm buf_ring ,
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.Nm buf_ring_alloc ,
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.Nm buf_ring_free ,
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.Nm buf_ring_enqueue ,
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.Nm buf_ring_dequeue_mc ,
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.Nm buf_ring_dequeue_sc ,
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.Nm buf_ring_count ,
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.Nm buf_ring_empty ,
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.Nm buf_ring_full ,
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.Nm buf_ring_peek ,
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.Nd multi-producer, {single, multi}-consumer lock-less ring buffer
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/buf_ring.h
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.Ft struct buf_ring *
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.Fn buf_ring_alloc "int count" "struct malloc_type *type" "int flags" "struct mtx *sc_lock"
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.Ft void
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.Fn buf_ring_free "struct buf_ring *br" "struct malloc_type *type"
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.Ft int
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.Fn buf_ring_enqueue "struct buf_ring *br" "void *buf"
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.Ft void *
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.Fn buf_ring_dequeue_mc "struct buf_ring *br"
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.Ft void *
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.Fn buf_ring_dequeue_sc "struct buf_ring *br"
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.Ft int
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.Fn buf_ring_count "struct buf_ring *br"
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.Ft int
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.Fn buf_ring_empty "struct buf_ring *br"
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.Ft int
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.Fn buf_ring_full "struct buf_ring *br"
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.Ft void *
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.Fn buf_ring_peek "struct buf_ring *br"
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.Sh DESCRIPTION
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The
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.Nm
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functions provide a lock-less multi-producer and lock-less multi-consumer as
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well as single-consumer ring buffer.
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.Pp
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The
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.Fn buf_ring_alloc
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function is used to allocate a buf_ring ring buffer with
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.Fa count
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slots using malloc_type
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.Fa type
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and memory flags
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.Fa flags .
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The single consumer interface is protected by
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.Fa sc_lock .
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.Pp
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The
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.Fn buf_ring_free
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function is used to free a buf_ring.
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The user is responsible for freeing any enqueued items.
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.Pp
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The
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.Fn buf_ring_enqueue
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function is used to enqueue a buffer to a buf_ring.
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.Pp
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The
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.Fn buf_ring_dequeue_mc
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function is a multi-consumer safe way of dequeueing elements from a buf_ring.
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.Pp
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The
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.Fn buf_ring_dequeue_sc
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function is a single-consumer interface to dequeue elements - requiring
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the user to serialize accesses with a lock.
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.Pp
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The
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.Fn buf_ring_count
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function returns the number of elements in a buf_ring.
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.Pp
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The
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.Fn buf_ring_empty
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function returns
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.Dv TRUE
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if the buf_ring is empty,
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.Dv FALSE
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otherwise.
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.Pp
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The
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.Fn buf_ring_full
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function returns
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.Dv TRUE
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if no more items can be enqueued,
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.Dv FALSE
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otherwise.
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.Pp
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The
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.Fn buf_ring_peek
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function returns a pointer to the last element in the buf_ring if the
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buf_ring is not empty,
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.Dv NULL
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otherwise.
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.Sh RETURN VALUES
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The
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.Fn buf_ring_enqueue
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function return
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.Er ENOBUFS
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if there are no available slots in the buf_ring.
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.Sh HISTORY
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These functions were introduced in
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.Fx 8.0 .
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