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While we are traversing the freelist anyways, merge a record
with the left if it is also a free list record.
That partially makes up for the fragmentation introduced by
the lack of merging with right records in tdb_free().
Note there is a potential slight downside:
If the left record we merge the current record into was earlier
in the chain and has hence already been met in traverse,
then we can not use the enlarged record even if it might be
a new best fit.
Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Thu Jun 26 12:16:03 CEST 2014 on sn-devel-104
So that we automatically defragment the free list when freelist_size is called
(unless the database is read only).
Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
This is intended to be called to reduce the fragmentation in the
freelist. This is to make up the deficiency of the freelist
to be not doubly linked. If the freelist were doubly linked,
we could easily avoid the creation of adjacent freelist entries.
But with the current singly linked list, it is only possible
to cheaply merge a new free record into a freelist entry on the left,
not on the right...
This can be called periodically, e.g. in the vacuuming process
of a ctdb cluster.
Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Variant of check_merge_with_left_record() that reads the record
itself if necessary.
Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Check whether the record left of a given freelist record is
also a freelist record, and if so, merge the two records.
Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
by using early returns and better variable names,
and reducing indentation.
Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
When in tdb_store we re-use a dead record reactivated from the
target hash chain itself, we currently leave it in its place in
the chain. When we re-use a dead record from a different chain or
from the freelist instead, we insert it at the beginning of the
target chain.
This patch changes the behaviour to always newly store a
record at the beginning of the hash chain. This removes
a special case and hence simplifies the allocation code.
On the other hand side, it introduces two additioal tdb_ofs_write
calls for the in-chain-case.
Note the subtelty of the patch that by moving the case of the candidate
record's chain as new case "i=0" into the for loop, we also reverse the
order of the two steps in the for-loop body (non blocking freelist alloc
and searching for dead record in a chain) in order to keep the overall
order of execution identical.
Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Michael Adam <obnox@samba.org>
Autobuild-Date(master): Wed Apr 9 10:37:08 CEST 2014 on sn-devel-104
In a metadata-intensive benchmark we have seen the locking.tdb freelist to be
one of the central contention points. This patch removes most of the contention
on the freelist. Ages ago we already reduced freelist contention by using the
even much older DEAD records: If TDB_VOLATILE is set, don't directly put
deleted records on the freelist, but just mark a few of them just as DEAD. The
next new record can them re-use that space without consulting the freelist.
This patch builds upon the DEAD records: If we need space and the freelist is
busy, instead of doing a blocking wait on the freelist, start looking into
other chains for DEAD records and steal them from there. This way every hash
chain becomes a small freelist. Just wander around the hash chains as long as
the freelist is still busy.
With this patch and the tdb mutex patch (following hopefully some time soon)
you can see a heavily busy clustered smbd run without locking.tdb futex
syscalls.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Michael Adam <obnox@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
We can have offsets > 2G, so use unsigned values. Fixes other prints to be
native types rather than casts, too.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Tue May 28 11:22:14 CEST 2013 on sn-devel-104
header.hash_size was the only thing we ever referenced outside of
tdb_open_ex and its direct callees. So this shrinks the tdb_context by
164 bytes.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Tue Feb 5 13:18:28 CET 2013 on sn-devel-104
methods->tdb_write expects data in on-disk format. For reading that
record, methods->tdb_read() has taken care of the on-disk to in-memory
representation according to the DOCONV() flag passed down. tdb_rec_write()
is a wrapper around methods->tdb_write just doing the CONVERT() on the
way to disk.
Reviewed-by: Rusty Russell <rusty@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
I came across a tdb which had wrapped to 4G + 4K, and the contents had been
destroyed by processes which thought it only 4k long. Fix this by checking
on open, and making tdb_oob() check for wrap itself.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Autobuild-User: Rusty Russell <rusty@rustcorp.com.au>
Autobuild-Date: Mon Dec 19 07:52:01 CET 2011 on sn-devel-104
It was a regrettable hack which I used to reduce line count in tdb; in fact it caused confusion as can be seen in this patch.
In particular, ecode now needs to be set before TDB_LOG anyway, and having it exposed in
the header is useless (the struct tdb_context isn't defined, so it's doubly useless).
Also, we should never set errno, as io.c was doing.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This greatly reduces the fragmentation of databases where records
tend to grow slowly by a small amount each time. The case where this
is most seen is the ldb index records. Adding this overallocation
reduced the size of the resulting database by more than 20x when
running a test that adds 10k users.
