git: ac503c194cd8 - main - Introduce "soft" serseq variant.
Alexander Motin
mav at FreeBSD.org
Tue Apr 6 21:28:16 UTC 2021
The branch main has been updated by mav:
URL: https://cgit.FreeBSD.org/src/commit/?id=ac503c194cd8e9dbef5c120e87f9521e1a89003a
commit ac503c194cd8e9dbef5c120e87f9521e1a89003a
Author: Alexander Motin <mav at FreeBSD.org>
AuthorDate: 2021-04-06 21:27:16 +0000
Commit: Alexander Motin <mav at FreeBSD.org>
CommitDate: 2021-04-06 21:27:16 +0000
Introduce "soft" serseq variant.
With new ZFS prefetcher improvements it is no longer needed to fully
serialize reads to reach decent prediction hit rate. Softer variant
only creates small time window to reduce races instead of completely
blocking following reads while previous is running. It much less
hurts the performance in case of prediction miss.
MFC after: 1 month
---
sys/cam/ctl/ctl.c | 3 ---
sys/cam/ctl/ctl_backend.h | 1 +
sys/cam/ctl/ctl_backend_block.c | 32 ++++++++++++++++++++++----------
sys/cam/ctl/ctl_backend_ramdisk.c | 5 ++++-
usr.sbin/ctladm/ctladm.8 | 9 +++++----
5 files changed, 32 insertions(+), 18 deletions(-)
diff --git a/sys/cam/ctl/ctl.c b/sys/cam/ctl/ctl.c
index cae6dd4aa101..575c8eea5198 100644
--- a/sys/cam/ctl/ctl.c
+++ b/sys/cam/ctl/ctl.c
@@ -13272,9 +13272,6 @@ ctl_serseq_done(union ctl_io *io)
{
struct ctl_lun *lun = CTL_LUN(io);
- if (lun->be_lun->serseq == CTL_LUN_SERSEQ_OFF)
- return;
-
/* This is racy, but should not be a problem. */
if (!TAILQ_EMPTY(&io->io_hdr.blocked_queue)) {
mtx_lock(&lun->lun_lock);
diff --git a/sys/cam/ctl/ctl_backend.h b/sys/cam/ctl/ctl_backend.h
index 05e65abe41f8..fe4e7f5df1d0 100644
--- a/sys/cam/ctl/ctl_backend.h
+++ b/sys/cam/ctl/ctl_backend.h
@@ -47,6 +47,7 @@
typedef enum {
CTL_LUN_SERSEQ_OFF,
+ CTL_LUN_SERSEQ_SOFT,
CTL_LUN_SERSEQ_READ,
CTL_LUN_SERSEQ_ON
} ctl_lun_serseq;
diff --git a/sys/cam/ctl/ctl_backend_block.c b/sys/cam/ctl/ctl_backend_block.c
index 9f96c157d5ae..4ffaf0912915 100644
--- a/sys/cam/ctl/ctl_backend_block.c
+++ b/sys/cam/ctl/ctl_backend_block.c
@@ -490,13 +490,12 @@ ctl_be_block_move_done(union ctl_io *io, bool samethr)
static void
ctl_be_block_biodone(struct bio *bio)
{
- struct ctl_be_block_io *beio;
- struct ctl_be_block_lun *be_lun;
+ struct ctl_be_block_io *beio = bio->bio_caller1;
+ struct ctl_be_block_lun *be_lun = beio->lun;
+ struct ctl_be_lun *cbe_lun = &be_lun->cbe_lun;
union ctl_io *io;
int error;
- beio = bio->bio_caller1;
- be_lun = beio->lun;
io = beio->io;
DPRINTF("entered\n");
@@ -576,7 +575,8 @@ ctl_be_block_biodone(struct bio *bio)
if ((ARGS(io)->flags & CTL_LLF_READ) &&
beio->beio_cont == NULL) {
ctl_set_success(&io->scsiio);
- ctl_serseq_done(io);
+ if (cbe_lun->serseq >= CTL_LUN_SERSEQ_SOFT)
+ ctl_serseq_done(io);
}
ctl_datamove(io);
}
@@ -636,6 +636,7 @@ static void
ctl_be_block_dispatch_file(struct ctl_be_block_lun *be_lun,
struct ctl_be_block_io *beio)
{
+ struct ctl_be_lun *cbe_lun = &be_lun->cbe_lun;
struct ctl_be_block_filedata *file_data;
union ctl_io *io;
struct uio xuio;
@@ -679,6 +680,9 @@ ctl_be_block_dispatch_file(struct ctl_be_block_lun *be_lun,
if (beio->bio_cmd == BIO_READ) {
vn_lock(be_lun->vn, LK_SHARED | LK_RETRY);
+ if (beio->beio_cont == NULL &&
+ cbe_lun->serseq == CTL_LUN_SERSEQ_SOFT)
+ ctl_serseq_done(io);
/*
* UFS pays attention to IO_DIRECT for reads. If the
* DIRECTIO option is configured into the kernel, it calls
@@ -786,7 +790,8 @@ ctl_be_block_dispatch_file(struct ctl_be_block_lun *be_lun,
if ((ARGS(io)->flags & CTL_LLF_READ) &&
beio->beio_cont == NULL) {
ctl_set_success(&io->scsiio);
- ctl_serseq_done(io);
+ if (cbe_lun->serseq > CTL_LUN_SERSEQ_SOFT)
+ ctl_serseq_done(io);
}
ctl_datamove(io);
}
@@ -863,6 +868,7 @@ static void
ctl_be_block_dispatch_zvol(struct ctl_be_block_lun *be_lun,
struct ctl_be_block_io *beio)
{
+ struct ctl_be_lun *cbe_lun = &be_lun->cbe_lun;
union ctl_io *io;
struct cdevsw *csw;
struct cdev *dev;
@@ -904,9 +910,12 @@ ctl_be_block_dispatch_zvol(struct ctl_be_block_lun *be_lun,
csw = devvn_refthread(be_lun->vn, &dev, &ref);
if (csw) {
- if (beio->bio_cmd == BIO_READ)
+ if (beio->bio_cmd == BIO_READ) {
+ if (beio->beio_cont == NULL &&
+ cbe_lun->serseq == CTL_LUN_SERSEQ_SOFT)
+ ctl_serseq_done(io);
error = csw->d_read(dev, &xuio, flags);
- else
+ } else
error = csw->d_write(dev, &xuio, flags);
dev_relthread(dev, ref);
} else
@@ -952,7 +961,8 @@ ctl_be_block_dispatch_zvol(struct ctl_be_block_lun *be_lun,
if ((ARGS(io)->flags & CTL_LLF_READ) &&
beio->beio_cont == NULL) {
ctl_set_success(&io->scsiio);
- ctl_serseq_done(io);
+ if (cbe_lun->serseq > CTL_LUN_SERSEQ_SOFT)
+ ctl_serseq_done(io);
}
ctl_datamove(io);
}
@@ -2187,12 +2197,14 @@ again:
ctl_be_block_close(be_lun);
cbe_lun->serseq = CTL_LUN_SERSEQ_OFF;
if (be_lun->dispatch != ctl_be_block_dispatch_dev)
- cbe_lun->serseq = CTL_LUN_SERSEQ_READ;
+ cbe_lun->serseq = CTL_LUN_SERSEQ_SOFT;
value = dnvlist_get_string(cbe_lun->options, "serseq", NULL);
if (value != NULL && strcmp(value, "on") == 0)
cbe_lun->serseq = CTL_LUN_SERSEQ_ON;
else if (value != NULL && strcmp(value, "read") == 0)
cbe_lun->serseq = CTL_LUN_SERSEQ_READ;
+ else if (value != NULL && strcmp(value, "soft") == 0)
+ cbe_lun->serseq = CTL_LUN_SERSEQ_SOFT;
else if (value != NULL && strcmp(value, "off") == 0)
cbe_lun->serseq = CTL_LUN_SERSEQ_OFF;
return (0);
diff --git a/sys/cam/ctl/ctl_backend_ramdisk.c b/sys/cam/ctl/ctl_backend_ramdisk.c
index e67d699bda70..6febdd469bdd 100644
--- a/sys/cam/ctl/ctl_backend_ramdisk.c
+++ b/sys/cam/ctl/ctl_backend_ramdisk.c
@@ -507,7 +507,8 @@ nospc:
if ((ARGS(io)->flags & CTL_LLF_READ) &&
ARGS(io)->len <= PRIV(io)->len) {
ctl_set_success(&io->scsiio);
- ctl_serseq_done(io);
+ if (cbe_lun->serseq >= CTL_LUN_SERSEQ_SOFT)
+ ctl_serseq_done(io);
}
ctl_datamove(io);
}
@@ -1036,6 +1037,8 @@ ctl_backend_ramdisk_create(struct ctl_be_ramdisk_softc *softc,
cbe_lun->serseq = CTL_LUN_SERSEQ_ON;
else if (value != NULL && strcmp(value, "read") == 0)
cbe_lun->serseq = CTL_LUN_SERSEQ_READ;
+ else if (value != NULL && strcmp(value, "soft") == 0)
+ cbe_lun->serseq = CTL_LUN_SERSEQ_SOFT;
else if (value != NULL && strcmp(value, "off") == 0)
cbe_lun->serseq = CTL_LUN_SERSEQ_OFF;
diff --git a/usr.sbin/ctladm/ctladm.8 b/usr.sbin/ctladm/ctladm.8
index 25380c86441a..b8b90ad200fe 100644
--- a/usr.sbin/ctladm/ctladm.8
+++ b/usr.sbin/ctladm/ctladm.8
@@ -1,6 +1,6 @@
.\"
.\" Copyright (c) 2003 Silicon Graphics International Corp.
-.\" Copyright (c) 2015-2020 Alexander Motin <mav at FreeBSD.org>
+.\" Copyright (c) 2015-2021 Alexander Motin <mav at FreeBSD.org>
.\" Copyright (c) 2018 Marcelo Araujo <araujo at FreeBSD.org>
.\" All rights reserved.
.\"
@@ -36,7 +36,7 @@
.\" $Id: //depot/users/kenm/FreeBSD-test2/usr.sbin/ctladm/ctladm.8#3 $
.\" $FreeBSD$
.\"
-.Dd November 23, 2020
+.Dd March 9, 2021
.Dt CTLADM 8
.Os
.Sh NAME
@@ -919,8 +919,9 @@ appropriate commands and task attributes.
The default value is "restricted".
It improves data integrity, but may introduce some additional delays.
.It Va serseq
-Set to "on" to serialize consecutive reads/writes.
-Set to "read" to serialize consecutive reads.
+Set to "on" to fully serialize consecutive reads/writes.
+Set to "read" to fully serialize consecutive reads.
+Set to "soft" to slightly serialize consecutive reads.
Set to "off" to allow them be issued in parallel.
Parallel issue of consecutive operations may confuse logic of the
backing file system, hurting performance; but it may improve performance
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