<div dir="ltr">No, I don't think so, "target_stripe > stripe" is another condition, but I do nothing here. If I use "else" the condition "target_strie > stripe" can not be handled. </div><div class="gmail_extra"> <div class="gmail_quote">2017-12-26 12:22 GMT+08:00 Randy Dunlap <<a href="mailto:rdunlap@infradead.org" target="_blank">rdunlap@infradead.org</a>>: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On 12/25/2017 07:52 PM, <a href="mailto:tgvlcw@gmail.com">tgvlcw@gmail.com</a> wrote: > From: liuchaowei <<a href="mailto:tgvlcw@gmail.com">tgvlcw@gmail.com</a>> > > This asymmetric stripe target device driver can achieve better io > performance between those devices which possess different io performance > > There are 2 storage device or flash devices: A and B, their sequential > read permance are 220M/s and 315M/s inspectively, so their sequential performance respectively, > read speed could be approximately equal to 2:3, if we use stripe type > to combine these two devices, their layout could be showed below: > -------------------------------------------------------- > | A1 | A2 | B1 | B2 | B3 | > -------------------------------------------------------- > > If we seletect asymmetric stripe type, their layout could be illustrated select > follow: > -------------------------------------------------------- > | A1 | B1 | > -------------------------------------------------------- > > The former has 5 stripe devices and each stripe device has also equal > chunk size, e.g.: 256secs. If there is a data block which size is > 1280secs, so transfer the data to this stripe defvice will be split device > to 5 ios which io size is 256secs. But if we use the asymmetric > stripe device, it only has two stripe devices and each one has be > setting in optimal chunk size, e.g.: ratio is 2:3, the first one > optimal chunk size is 512secs, the second is 768secs. And same > 1280secs data block just only be splited two ios, this can be achieve split into two ios, > perfect io performance. > > Change-Id: Iebaee3480e27022e2b3a7edbfb65425b1166274e > Signed-off-by: liuchaowei <<a href="mailto:tgvlcw@gmail.com">tgvlcw@gmail.com</a>> > --- > Documentation/device-mapper/asymmetric-striped.txt | 85 ++++ > drivers/md/Kconfig | 11 + > drivers/md/Makefile | 1 + > drivers/md/dm-asymmetric-stripe.c | 523 +++++++++++++++++++++ > drivers/md/dm.c | 5 + > include/linux/device-mapper.h | 15 + > 6 files changed, 640 insertions(+) > create mode 100644 Documentation/device-mapper/asymmetric-striped.txt > create mode 100644 drivers/md/dm-asymmetric-stripe.c > > diff --git a/Documentation/device-mapper/asymmetric-striped.txt b/Documentation/device-mapper/asymmetric-striped.txt > new file mode 100644 > index 000000000000..0412a224a49e > --- /dev/null > +++ b/Documentation/device-mapper/asymmetric-striped.txt > @@ -0,0 +1,85 @@ > +dm-asymmetric-stripe > +========= > + > +Device-Mapper's "asm-striped" target is used to create a striped (i.e. RAID-0) > +device across one or more underlying devices. Data is written in "chunks", > +with consecutive chunks rotating among the underlying devices. This can > +potentially provide improved I/O throughput by utilizing several physical > +devices in parallel. However, in order to gain maximum I/O performance bewteen between > +slow and fast device, there is a ratio to set up the chunk size among these > +device. > + > +Parameters: <num devs> <chunk size> <ratio> [<dev path> <offset>]+ > +<num devs>: Number of underlying devices. > +<chunk size>: Size of each chunk of data. Must be at least as > +large as the system's PAGE_SIZE. > +<ratio>: The proportion of per io size, it is the times as much > +as 1 chunk size > +<dev path>: Full pathname to the underlying block-device, or a > +"major:minor" device-number. > +<offset>: Starting sector within the device. > + > +One or more underlying devices can be specified. The striped device > +size must be a multiple of the chunk size multiplied by the number of underlying > +devices. However, there is a ratio can be setting, e.g.: 2:3 means the first one there is a ratio that can be set, > +striped device optimal width size is 2 time as much as 1 chunk size, the second times > +striped device is 3. > + > + > +Example scripts > +=============== > + > +[[ > +#!/usr/bin/perl -w > +# Create a striped device across any number of underlying devices. The device > +# will be called "stripe_dev" and have a chunk-size of 128k. > + > +my $chunk_size = 128 * 2; > +my $ratio = "2:3"; > +my $dev_name = "stripe_dev"; > +my $num_devs = @ARGV; > +my @devs = @ARGV; > + > +if ($num_devs < 2) { > +die("Specify at least two devices\n"); > +} > + > + > +$stripe_average_size = 1073741824 > +$stripe_dev_size = $stripe_average_size * 5; > + > +$table = "0 $stripe_dev_size asm-striped $num_devs $chunk_size $ratio"; > +for ($i = 0; $i < $num_devs; $i++) { > +$table .= " $devs[$i] 0"; > +} > + > +`echo $table | dmsetup create $dev_name`; > +]] > + > + > +Why asymmetric striped > +======================= > +Considering one case: > +There are 2 storage device or flash devices: A and B, their sequential > +read permance are 220M/s and 315M/s inspectively, so their sequential performance respectively, > +read speed could be approximately equal to 2:3, if we use stripe type > +to combine these two devices, their layout could be showed below: > +-------------------------------------------------------- > +| A1 | A2 | B1 | B2 | B3 | > +-------------------------------------------------------- > + > +If we seletect asymmetric stripe type, their layout could be illustrated select > +follow: > +-------------------------------------------------------- > +| A1 | B1 | > +-------------------------------------------------------- > + > +The former has 5 stripe devices and each stripe device has also equal > +chunk size, e.g.: 256secs. If there is a data block which size is 1280secs, > +so transfer the data to this stripe defvice will be split to 5 ios which io device > +size is 256secs. But if we use the asymmetric stripe device, it only has two > +stripe devices and each one has be setting in optimal chunk size, e.g.: ratio > +is 2:3, the first one optimal chunk size is 512secs, the second is 768secs. > +And same 1280secs data block just only be splited two ios, this can be achieve split into two ios, > +perfect io performance. > + > diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig > index 7d5aa2c5c81d..4232b929c2f3 100644 > --- a/drivers/md/Kconfig > +++ b/drivers/md/Kconfig > @@ -455,6 +455,17 @@ config DM_FLAKEY > ---help--- > A target that intermittently fails I/O for debugging purposes. > > +config DM_ASYMMETRIC_STRIPE > + tristate "DM asymmetric stripe(asymmetric raid0)" > + depends on BLK_DEV_DM > + ---help--- > + This device-mapper target creates a asymmetric raid0/stripe device that > + support asymmetric stripe chunk size and can gain same performance as > + raid0 device Align "support" and "raid0" under "This". And end the sentence with a period ("."). > + > + You must configure the accurate ratio between different physical storage > + device respectively End sentence with a period. > + > config DM_VERITY > tristate "Verity target support" > depends on BLK_DEV_DM > diff --git a/drivers/md/dm-asymmetric-stripe.c b/drivers/md/dm-asymmetric-stripe.c > new file mode 100644 > index 000000000000..4ef3915b435a > --- /dev/null > +++ b/drivers/md/dm-asymmetric-stripe.c > @@ -0,0 +1,523 @@ > +/* > + * Copyright (C) 2018 Smartisan, Inc. > + * > + * This software is licensed under the terms of the GNU General Public > + * License version 2, as published by the Free Software Foundation, and > + * may be copied, distributed, and modified under those terms. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * Author: <<a href="mailto:tgvlcw@gmail.com">tgvlcw@gmail.com</a>> > + * Name: Henry Liu > + * > + */ > + > + > +#include "dm.h" > +#include <linux/device-mapper.h> > + #include <linux/atomic.h> > +#include <linux/module.h> > +#include <linux/init.h> #include <linux/kernel.h> > +#include <linux/blkdev.h> > +#include <linux/bio.h> #include <linux/bitops.h> > +#include <linux/slab.h> > +#include <linux/log2.h> #include <linux/workqueue.h> > + > +#define DM_MSG_PREFIX "asm-striped" > +#define DM_IO_ERROR_THRESHOLD 15 > +/* > + * An event is triggered whenever a drive > + * drops out of a stripe volume. > + */ > +static void trigger_event(struct work_struct *work) > +{ > + asm_stripe_c *sc = container_of(work, asm_stripe_c, trigger_event); > + > + dm_table_event(sc->ti->table); > +} > + > + static inline Above line should not be indented. Above and below should be on one line if <= 80 characters. > +asm_stripe_c *alloc_context(unsigned int stripes) > +{ > + size_t len; > + > + if (dm_array_too_big(sizeof(asm_stripe_c), > + sizeof(asm_stripe), > + stripes)) > + return NULL; > + > + len = sizeof(asm_stripe_c) + (sizeof(asm_stripe) * stripes); > + > + return kmalloc(len, GFP_KERNEL); > +} > +static int set_stripe_ratio(struct dm_target *ti, > + asm_stripe_c *sc, > + char *ratio_str) > +{ > + char *p; > + unsigned int i; > + uint32_t r = 0, ratio; > + char *tmp_ratio = ratio_str; > + > + if (sizeof(sc->ratio_str) < strlen(ratio_str)) { > + ti->error = "Too big stripe ratio string"; > + return -ENOMEM; > + } > + > + strlcpy(sc->ratio_str, ratio_str, strlen(ratio_str) + 1); > + for (i = 0; i < sc->stripes; i++) { > + p = strsep(&tmp_ratio, ":"); > + if (p == NULL) > + return -EINVAL; > + > + if (kstrtouint(p, 10, &ratio) || !ratio) > + return -EINVAL; > + > + sc->stripe[i].ratio = ratio; > + r += ratio; > + } > + > + sc->total_ratio = r; > + sc->avg_width = ti->len / r; > + sc->stripe_size = r * sc->chunk_size; > + > + return 0; > +} Insert blank line here. > +/* > + * Construct a striped mapping. > + * <number of stripes> <chunk size> <ratio> [<dev_path> <offset>]+ > + */ > +static int asymmetric_stripe_ctr(struct dm_target *ti, > + unsigned int argc, > + char **argv) > +{ [snip] > +static void asymmetric_stripe_map_range_sector(asm_stripe_c *sc, > + sector_t sector, > + uint32_t target_stripe, > + sector_t *result) > +{ > + sector_t width_offset; > + uint32_t stripe; > + > + width_offset = stripe_index_fetch(sc, &sector, &stripe); > + > + *result = sector * sc->stripe[target_stripe].opt_io_size; > + > + if (target_stripe < stripe) > + *result += sc->stripe[target_stripe].opt_io_size; > + else if (target_stripe == stripe) > + *result += width_offset; Here you don't expect target_stripe ever to be > stripe, right? Then the last "else if" can just be "else"... > +} > + -- ~Randy </blockquote></div> </div>