Date: Thu, 3 Dec 2015 13:13:25 -0800 From: Bryan Drewery <bdrewery@FreeBSD.org> To: "Kenneth D. Merry" <ken@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r291716 - in head: share/man/man4 sys/cam sys/cam/ata sys/cam/scsi sys/dev/md sys/geom sys/kern sys/pc98/include sys/sys usr.sbin usr.sbin/camdd Message-ID: <5660B075.8040806@FreeBSD.org> In-Reply-To: <201512032054.tB3KsuUw037541@repo.freebsd.org> References: <201512032054.tB3KsuUw037541@repo.freebsd.org>
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On 12/3/15 12:54 PM, Kenneth D. Merry wrote: > Author: ken > Date: Thu Dec 3 20:54:55 2015 > New Revision: 291716 > URL: https://svnweb.freebsd.org/changeset/base/291716 > > Log: > Add asynchronous command support to the pass(4) driver, and the new > camdd(8) utility. > > CCBs may be queued to the driver via the new CAMIOQUEUE ioctl, and > completed CCBs may be retrieved via the CAMIOGET ioctl. User > processes can use poll(2) or kevent(2) to get notification when > I/O has completed. > > While the existing CAMIOCOMMAND blocking ioctl interface only > supports user virtual data pointers in a CCB (generally only > one per CCB), the new CAMIOQUEUE ioctl supports user virtual and > physical address pointers, as well as user virtual and physical > scatter/gather lists. This allows user applications to have more > flexibility in their data handling operations. > > Kernel memory for data transferred via the queued interface is > allocated from the zone allocator in MAXPHYS sized chunks, and user > data is copied in and out. This is likely faster than the > vmapbuf()/vunmapbuf() method used by the CAMIOCOMMAND ioctl in > configurations with many processors (there are more TLB shootdowns > caused by the mapping/unmapping operation) but may not be as fast > as running with unmapped I/O. > > The new memory handling model for user requests also allows > applications to send CCBs with request sizes that are larger than > MAXPHYS. The pass(4) driver now limits queued requests to the I/O > size listed by the SIM driver in the maxio field in the Path > Inquiry (XPT_PATH_INQ) CCB. > > There are some things things would be good to add: > > 1. Come up with a way to do unmapped I/O on multiple buffers. > Currently the unmapped I/O interface operates on a struct bio, > which includes only one address and length. It would be nice > to be able to send an unmapped scatter/gather list down to > busdma. This would allow eliminating the copy we currently do > for data. > > 2. Add an ioctl to list currently outstanding CCBs in the various > queues. > > 3. Add an ioctl to cancel a request, or use the XPT_ABORT CCB to do > that. > > 4. Test physical address support. Virtual pointers and scatter > gather lists have been tested, but I have not yet tested > physical addresses or scatter/gather lists. > > 5. Investigate multiple queue support. At the moment there is one > queue of commands per pass(4) device. If multiple processes > open the device, they will submit I/O into the same queue and > get events for the same completions. This is probably the right > model for most applications, but it is something that could be > changed later on. > > Also, add a new utility, camdd(8) that uses the asynchronous pass(4) > driver interface. > > This utility is intended to be a basic data transfer/copy utility, > a simple benchmark utility, and an example of how to use the > asynchronous pass(4) interface. > > It can copy data to and from pass(4) devices using any target queue > depth, starting offset and blocksize for the input and ouptut devices. > It currently only supports SCSI devices, but could be easily extended > to support ATA devices. > > It can also copy data to and from regular files, block devices, tape > devices, pipes, stdin, and stdout. It does not support queueing > multiple commands to any of those targets, since it uses the standard > read(2)/write(2)/writev(2)/readv(2) system calls. > > The I/O is done by two threads, one for the reader and one for the > writer. The reader thread sends completed read requests to the > writer thread in strictly sequential order, even if they complete > out of order. That could be modified later on for random I/O patterns > or slightly out of order I/O. > > camdd(8) uses kqueue(2)/kevent(2) to get I/O completion events from > the pass(4) driver and also to send request notifications internally. > > For pass(4) devcies, camdd(8) uses a single buffer (CAM_DATA_VADDR) > per CAM CCB on the reading side, and a scatter/gather list > (CAM_DATA_SG) on the writing side. In addition to testing both > interfaces, this makes any potential reblocking of I/O easier. No > data is copied between the reader and the writer, but rather the > reader's buffers are split into multiple I/O requests or combined > into a single I/O request depending on the input and output blocksize. > > For the file I/O path, camdd(8) also uses a single buffer (read(2), > write(2), pread(2) or pwrite(2)) on reads, and a scatter/gather list > (readv(2), writev(2), preadv(2), pwritev(2)) on writes. > > Things that would be nice to do for camdd(8) eventually: > > 1. Add support for I/O pattern generation. Patterns like all > zeros, all ones, LBA-based patterns, random patterns, etc. Right > Now you can always use /dev/zero, /dev/random, etc. > > 2. Add support for a "sink" mode, so we do only reads with no > writes. Right now, you can use /dev/null. > > 3. Add support for automatic queue depth probing, so that we can > figure out the right queue depth on the input and output side > for maximum throughput. At the moment it defaults to 6. > > 4. Add support for SATA device passthrough I/O. > > 5. Add support for random LBAs and/or lengths on the input and > output sides. > > 6. Track average per-I/O latency and busy time. The busy time > and latency could also feed in to the automatic queue depth > determination. > > sys/cam/scsi/scsi_pass.h: > Define two new ioctls, CAMIOQUEUE and CAMIOGET, that queue > and fetch asynchronous CAM CCBs respectively. > > Although these ioctls do not have a declared argument, they > both take a union ccb pointer. If we declare a size here, > the ioctl code in sys/kern/sys_generic.c will malloc and free > a buffer for either the CCB or the CCB pointer (depending on > how it is declared). Since we have to keep a copy of the > CCB (which is fairly large) anyway, having the ioctl malloc > and free a CCB for each call is wasteful. > > sys/cam/scsi/scsi_pass.c: > Add asynchronous CCB support. > > Add two new ioctls, CAMIOQUEUE and CAMIOGET. > > CAMIOQUEUE adds a CCB to the incoming queue. The CCB is > executed immediately (and moved to the active queue) if it > is an immediate CCB, but otherwise it will be executed > in passstart() when a CCB is available from the transport layer. > > When CCBs are completed (because they are immediate or > passdone() if they are queued), they are put on the done > queue. > > If we get the final close on the device before all pending > I/O is complete, all active I/O is moved to the abandoned > queue and we increment the peripheral reference count so > that the peripheral driver instance doesn't go away before > all pending I/O is done. > > The new passcreatezone() function is called on the first > call to the CAMIOQUEUE ioctl on a given device to allocate > the UMA zones for I/O requests and S/G list buffers. This > may be good to move off to a taskqueue at some point. > The new passmemsetup() function allocates memory and > scatter/gather lists to hold the user's data, and copies > in any data that needs to be written. For virtual pointers > (CAM_DATA_VADDR), the kernel buffer is malloced from the > new pass(4) driver malloc bucket. For virtual > scatter/gather lists (CAM_DATA_SG), buffers are allocated > from a new per-pass(9) UMA zone in MAXPHYS-sized chunks. > Physical pointers are passed in unchanged. We have support > for up to 16 scatter/gather segments (for the user and > kernel S/G lists) in the default struct pass_io_req, so > requests with longer S/G lists require an extra kernel malloc. > > The new passcopysglist() function copies a user scatter/gather > list to a kernel scatter/gather list. The number of elements > in each list may be different, but (obviously) the amount of data > stored has to be identical. > > The new passmemdone() function copies data out for the > CAM_DATA_VADDR and CAM_DATA_SG cases. > > The new passiocleanup() function restores data pointers in > user CCBs and frees memory. > > Add new functions to support kqueue(2)/kevent(2): > > passreadfilt() tells kevent whether or not the done > queue is empty. > > passkqfilter() adds a knote to our list. > > passreadfiltdetach() removes a knote from our list. > > Add a new function, passpoll(), for poll(2)/select(2) > to use. > > Add devstat(9) support for the queued CCB path. > > sys/cam/ata/ata_da.c: > Add support for the BIO_VLIST bio type. > > sys/cam/cam_ccb.h: > Add a new enumeration for the xflags field in the CCB header. > (This doesn't change the CCB header, just adds an enumeration to > use.) > > sys/cam/cam_xpt.c: > Add a new function, xpt_setup_ccb_flags(), that allows specifying > CCB flags. > > sys/cam/cam_xpt.h: > Add a prototype for xpt_setup_ccb_flags(). > > sys/cam/scsi/scsi_da.c: > Add support for BIO_VLIST. > > sys/dev/md/md.c: > Add BIO_VLIST support to md(4). > > sys/geom/geom_disk.c: > Add BIO_VLIST support to the GEOM disk class. Re-factor the I/O size > limiting code in g_disk_start() a bit. > > sys/kern/subr_bus_dma.c: > Change _bus_dmamap_load_vlist() to take a starting offset and > length. > > Add a new function, _bus_dmamap_load_pages(), that will load a list > of physical pages starting at an offset. > > Update _bus_dmamap_load_bio() to allow loading BIO_VLIST bios. > Allow unmapped I/O to start at an offset. > > sys/kern/subr_uio.c: > Add two new functions, physcopyin_vlist() and physcopyout_vlist(). > > sys/pc98/include/bus.h: > Guard kernel-only parts of the pc98 machine/bus.h header with > #ifdef _KERNEL. > > This allows userland programs to include <machine/bus.h> to get the > definition of bus_addr_t and bus_size_t. > > sys/sys/bio.h: > Add a new bio flag, BIO_VLIST. > > sys/sys/uio.h: > Add prototypes for physcopyin_vlist() and physcopyout_vlist(). > > share/man/man4/pass.4: > Document the CAMIOQUEUE and CAMIOGET ioctls. > > usr.sbin/Makefile: > Add camdd. > > usr.sbin/camdd/Makefile: > Add a makefile for camdd(8). > > usr.sbin/camdd/camdd.8: > Man page for camdd(8). > > usr.sbin/camdd/camdd.c: > The new camdd(8) utility. > > Sponsored by: Spectra Logic > MFC after: 1 week > > Added: > head/usr.sbin/camdd/ > head/usr.sbin/camdd/Makefile (contents, props changed) > +++ usr.sbin/camdd/Makefile > @@ -0,0 +1,11 @@ > +# $FreeBSD$ > + > +PROG= camdd > +SRCS= camdd.c > +SDIR= ${.CURDIR}/../../sys > +DPADD= ${LIBCAM} ${LIBMT} ${LIBSBUF} ${LIBBSDXML} ${LIBUTIL} ${LIBTHR} > +LDADD= -lcam -lmt -lsbuf -lbsdxml -lutil -lthr We use LIBADD in head now, not DPADD and LDADD. See r291718. -- Regards, Bryan Drewery
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