On 09/06/14 09:25, Olivier Mascia o...@tipgroup.com [firebird-support] wrote:
I am seeing 45 seconds for a 13Mb file using C++ / IBPP and 48
seconds using PHP.
Exactly the same code, database structure and hardware on Windows
inserts a 13Mb BLOB in just 2.4 seconds!
That just means the caching/flushing policy is different on both OSes.
I don't know the current state of implementation of sync-writes in
linux versions of Firebird. Nor its relationship with OS filesystem
cache. But reading about firebird.conf parameters
FileSystemCacheThreshold, FileSystemCacheSize, MaxUnflushedWrites,
MaxUnflushedWriteTimes, and synced / not-synced writes (database
setting), will be a good starting point.
Olivier, thank you for your insightful reply here and on the
IBPP-DISCUSS mailing list
http://sourceforge.net/p/ibpp/mailman/message/32435680/.
This was indeed the reason for such a big difference, in fact Linux is
now about twice the speed of Windows 8 (approximately 1.3 secs for 13Mb
file), although this may not be like-for-like configuration parameters
(the Windows system is still using the default firebird.conf).
Based on your comments and other information I did the following on Linux:
1. Uncomment the MaxUnflushedWrites and MaxUnflushedWriteTimes in
firebird.conf (i.e. with values 100 and 5 respectively).
2. Make a backup of the database and restore it with a larger page size:
gbak -replace test.fbk test.fdb -page_size 16384 -v -user sysdba
-password secret.
3. Set the database mode to be asynchronous with:
gfix -write async test.fdb -user sysdba -password secret
These tests were made using the embedded server and FlameRobin which I
believe writes blobs in 32768 byte segments.
So the only mystery (for me!) remaining is why the UDF is so much faster
when it is writing 4096 bytes at time with forced writes on?
Thanks again ... Mike.
