Sqlite experts,
I am running Sqlite version 3.4.1. I ran some performance tests and
observed that sqlite sometimes consumes more CPU than normal (I am
using same dataset, all inserts and recreating new database for each
test). Tried running oprofiile and got the following result. The
function 'syncJournal' is taking around 60% of total Sqlite's CPU
usage.
1. Is this normal behaviour? If not, is there a known fix for this?
2. Are there any tunables that can be used to ease the issue?
PS: My database is pretty small. I am setting max_page_count=896 and
page_size = 512 (Max database size = 3.5MB).
Thanks in advance.
******** OPANNOTATE output ******************
:static int syncJournal(Pager *pPager){ /* syncJournal
total: 2815 23.5034 */
: PgHdr *pPg;
: int rc = SQLITE_OK;
: : /* Sync the journal before modifying
the main database
: ** (assuming there is a journal and it needs to be synced.)
: */ : if( pPager->needSync ){
: if( !pPager->tempFile ){
: assert( pPager->journalOpen );
: /* assert( !pPager->noSync ); // noSync might be
set if synchronous
: ** was turned off after the transaction was
started. Ticket #615 */
:#ifndef NDEBUG
: {
: /* Make sure the pPager->nRec counter we are
keeping agrees
: ** with the nRec computed from the size of the
journal file.
: */
: i64 jSz;
: rc = sqlite3OsFileSize(pPager->jfd, &jSz);
: if( rc!=0 ) return rc;
: assert( pPager->journalOff==jSz );
: }
:#endif
: {
: /* Write the nRec value into the journal file
header. If in
: ** full-synchronous mode, sync the journal
first. This ensures that
: ** all data has really hit the disk before
nRec is updated to mark
: ** it as a candidate for rollback.
: */
2 0.0167 : if( pPager->fullSync ){
: PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
: IOTRACE(("JSYNC %p\n", pPager))
7 0.0584 : rc = sqlite3OsSync(pPager->jfd, 0);
1 0.0083 : if( rc!=0 ) return rc;
: }
1 0.0083 : rc = sqlite3OsSeek(pPager->jfd,
: pPager->journalHdr +
sizeof(aJournalMagic));
: if( rc ) return rc;
: IOTRACE(("JHDR %p %lld %d\n", pPager,
: pPager->journalHdr +
sizeof(aJournalMagic), 4))
1 0.0083 : rc = write32bits(pPager->jfd, pPager->nRec);
: if( rc ) return rc;
:
: rc = sqlite3OsSeek(pPager->jfd, pPager->journalOff);
: if( rc ) return rc;
: }
: PAGERTRACE2("SYNC journal of %d\n", PAGERID(pPager));
: IOTRACE(("JSYNC %p\n", pPager))
1 0.0083 : rc = sqlite3OsSync(pPager->jfd, pPager->full_fsync);
4 0.0334 : if( rc!=0 ) return rc;
: pPager->journalStarted = 1;
: }
: pPager->needSync = 0;
:
: /* Erase the needSync flag from every page.
: */
2716 22.6768 : for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
79 0.6596 : pPg->needSync = 0;
: }
2 0.0167 : pPager->pFirstSynced = pPager->pFirst;
: }
:#ifndef NDEBUG
: /* If the Pager.needSync flag is clear then the PgHdr.needSync
: ** flag must also be clear for all pages. Verify that this
: ** invariant is true.
: */
: else{
: for(pPg=pPager->pAll; pPg; pPg=pPg->pNextAll){
: assert( pPg->needSync==0 );
: }
: assert( pPager->pFirstSynced==pPager->pFirst );
: }
:#endif
:
: return rc;
1 0.0083 :}
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