When safety requirements are met, it allows to avoid passing I/O requests
to GEOM g_up/g_down thread, executing them directly in the caller context.
That allows to avoid CPU bottlenecks in g_up/g_down threads, plus avoid
several context switches per I/O.
The defined now safety requirements are:
- caller should not hold any locks and should be reenterable;
- callee should not depend on GEOM dual-threaded concurency semantics;
- on the way down, if request is unmapped while callee doesn't support it,
the context should be sleepable;
- kernel thread stack usage should be below 50%.
To keep compatibility with GEOM classes not meeting above requirements
new provider and consumer flags added:
- G_CF_DIRECT_SEND -- consumer code meets caller requirements (request);
- G_CF_DIRECT_RECEIVE -- consumer code meets callee requirements (done);
- G_PF_DIRECT_SEND -- provider code meets caller requirements (done);
- G_PF_DIRECT_RECEIVE -- provider code meets callee requirements (request).
Capable GEOM class can set them, allowing direct dispatch in cases where
it is safe. If any of requirements are not met, request is queued to
g_up or g_down thread same as before.
Such GEOM classes were reviewed and updated to support direct dispatch:
CONCAT, DEV, DISK, GATE, MD, MIRROR, MULTIPATH, NOP, PART, RAID, STRIPE,
VFS, ZERO, ZFS::VDEV, ZFS::ZVOL, all classes based on g_slice KPI (LABEL,
MAP, FLASHMAP, etc).
To declare direct completion capability disk(9) KPI got new flag equivalent
to G_PF_DIRECT_SEND -- DISKFLAG_DIRECT_COMPLETION. da(4) and ada(4) disk
drivers got it set now thanks to earlier CAM locking work.
This change more then twice increases peak block storage performance on
systems with manu CPUs, together with earlier CAM locking changes reaching
more then 1 million IOPS (512 byte raw reads from 16 SATA SSDs on 4 HBAs to
256 user-level threads).
Sponsored by: iXsystems, Inc.
MFC after: 2 months
The SYSCTL_NODE macro defines a list that stores all child-elements of
that node. If there's no SYSCTL_DECL macro anywhere else, there's no
reason why it shouldn't be static.
Do not close/destroy opened consumer directly in case of disconnect. Instead
keep it existing until it will be closed in regular way in response to
upstream provider destruction. Delay geom destruction in the same way.
Previous implementation could destroy consumers still having active
requests and worked only because of global workaround made on GEOM level.
No FreeBSD version bump, the userland application to query the features will
be committed last and can serve as an indication of the availablility if
needed.
Sponsored by: Google Summer of Code 2010
Submitted by: kibab
Reviewed by: silence on geom@ during 2 weeks
X-MFC after: to be determined in last commit with code from this project
depend on on-disk metadata. This was we won't attach to providers that are used
by other classes. For example we don't want to configure partitions on da0 if
it is part of gmirror, what we really want is partitions on mirror/foo.
During regular work it works like this: if provider is open for writing a class
receives the spoiled event from GEOM and detaches, once provider is closed the
taste event is send again and class can rediscover its metadata if it is still
there. This doesn't work that way when new class arrives, because GEOM gives
all existing providers for it to taste, also those open for writing. Classes
have to decided on their own if they want to deal with such providers (eg.
geom_dev) or not (classes modified by this commit).
Reported by: des, Oliver Lehmann <lehmann@ans-netz.de>
Tested by: des, Oliver Lehmann <lehmann@ans-netz.de>
Discussed with: phk, marcel
Reviewed by: marcel
MFC after: 3 days
- Prefer '_' to ' ', as it results in more easily parsed results in
memory monitoring tools such as vmstat.
- Remove punctuation that is incompatible with using memory type names
as file names, such as '/' characters.
- Disambiguate some collisions by adding subsystem prefixes to some
memory types.
- Generally prefer lower case to upper case.
- If the same type is defined in multiple architecture directories,
attempt to use the same name in additional cases.
Not all instances were caught in this change, so more work is required to
finish this conversion. Similar changes are required for UMA zone names.
completed I/O requests here.
- First allocate all needed bios, so if any of allocations fail, we can
free memory before sending any I/O requests down.
Reported by: Pawel Malachowski
MFC after: 3 days
shared-last-sector problem.
After this change, even if there is more than one provider with the same
last sector, the proper one will be chosen based on its size.
It still doesn't fix the 'c' partition problem (when da0s1 can be confused
with da0s1c) and situation when 'a' partition starts at offset 0
(then da0s1a can be confused with da0s1 and da0s1c). One can use '-h'
option there, when creating device or avoid sharing last sector.
Actually, when providers share the same last sector and their size is equal,
they provide exactly the same data, so the name (da0s1, da0s1a, da0s1c)
isn't important at all.
- Provide backward compatibility.
- Update copyright's year.
MFC after: 1 week
Actually, it can even cause some problems, because GEOM requires sectorsize
to be more than 0 on first access, not on provider creation, so we can skip
valid providers by doing this check here.
Reported by: Divacky Roman <xdivac02@stud.fit.vutbr.cz>
Sven Willenberger <sven@dmv.com>
It allows to fix problems when last provider's sector is shared between few
providers.
- Bump version number for CONCAT and STRIPE and add code for backward
compatibility.
- Do not bump version number of MIRROR, as it wasn't officially introduced yet.
Even if someone started to play with it, there is no big deal, because
wrong MD5 sum of metadata will deny those providers.
- Update manual pages.
- Add version history to g_(stripe|concat).h files.
least common multiple of all disks sector sizes.
This will allow to safely concatenate disks with different sector sizes.
- Mark unused function arguments.
- Other minor cleanups.
