mp_trickle.c

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/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 1996, 1997, 1998, 1999, 2000
 *      Sleepycat Software.  All rights reserved.
 */
#include "config.h"

#ifndef lint
static const char revid[] = "$Id: mp__trickle_8c-source.html,v 1.1 2008/06/08 10:20:54 sebdiaz Exp $";
#endif /* not lint */

#ifndef NO_SYSTEM_INCLUDES
#include <sys/types.h>

#include <errno.h>
#include <stdlib.h>
#endif

#ifdef  HAVE_RPC
#include "db_server.h"
#endif

#include "db_int.h"
#include "db_shash.h"
#include "mp.h"

#ifdef HAVE_RPC
#include "gen_client_ext.h"
#include "rpc_client_ext.h"
#endif

static int __memp_trick __P((DB_ENV *, int, int, int *));

/*
 * CDB_memp_trickle --
 *      Keep a specified percentage of the buffers clean.
 */
int
CDB_memp_trickle(dbenv, pct, nwrotep)
        DB_ENV *dbenv;
        int pct, *nwrotep;
{
        DB_MPOOL *dbmp;
        MPOOL *mp;
        u_int32_t i;
        int ret;

#ifdef HAVE_RPC
        if (F_ISSET(dbenv, DB_ENV_RPCCLIENT))
                return (__dbcl_memp_trickle(dbenv, pct, nwrotep));
#endif

        PANIC_CHECK(dbenv);
        ENV_REQUIRES_CONFIG(dbenv, dbenv->mp_handle, DB_INIT_MPOOL);

        dbmp = dbenv->mp_handle;
        mp = dbmp->reginfo[0].primary;

        if (nwrotep != NULL)
                *nwrotep = 0;

        if (pct < 1 || pct > 100)
                return (EINVAL);

        R_LOCK(dbenv, dbmp->reginfo);

        /* Loop through the caches... */
        for (ret = 0, i = 0; i < mp->nreg; ++i)
                if ((ret = __memp_trick(dbenv, i, pct, nwrotep)) != 0)
                        break;

        R_UNLOCK(dbenv, dbmp->reginfo);
        return (ret);
}

/*
 * __memp_trick --
 *      Trickle a single cache.
 */
static int
__memp_trick(dbenv, ncache, pct, nwrotep)
        DB_ENV *dbenv;
        int ncache, pct, *nwrotep;
{
        BH *bhp;
        DB_MPOOL *dbmp;
        MPOOL *c_mp;
        MPOOLFILE *mfp;
        db_pgno_t pgno;
        u_long total;
        int ret, wrote;

        dbmp = dbenv->mp_handle;
        c_mp = dbmp->reginfo[ncache].primary;

        /*
         * If there are sufficient clean buffers, or no buffers or no dirty
         * buffers, we're done.
         *
         * XXX
         * Using st_page_clean and st_page_dirty is our only choice at the
         * moment, but it's not as correct as we might like in the presence
         * of pools with more than one buffer size, as a free 512-byte buffer
         * isn't the same as a free 8K buffer.
         */
loop:   total = c_mp->stat.st_page_clean + c_mp->stat.st_page_dirty;
        if (total == 0 || c_mp->stat.st_page_dirty == 0 ||
            (c_mp->stat.st_page_clean * 100) / total >= (u_long)pct)
                return (0);

        /* Loop until we write a buffer. */
        for (bhp = SH_TAILQ_FIRST(&c_mp->bhq, __bh);
            bhp != NULL; bhp = SH_TAILQ_NEXT(bhp, q, __bh)) {
                if (bhp->ref != 0 ||
                    !F_ISSET(bhp, BH_DIRTY) || F_ISSET(bhp, BH_LOCKED))
                        continue;

                mfp = R_ADDR(dbmp->reginfo, bhp->mf_offset);

                /*
                 * We can't write to temporary files -- see the comment in
                 * mp_bh.c:CDB___memp_bhwrite().
                 */
                if (F_ISSET(mfp, MP_TEMP))
                        continue;

                pgno = bhp->pgno;
                if ((ret = CDB___memp_bhwrite(dbmp, mfp, bhp, NULL, &wrote)) != 0)
                        return (ret);

                /*
                 * Any process syncing the shared memory buffer pool had better
                 * be able to write to any underlying file.  Be understanding,
                 * but firm, on this point.
                 */
                if (!wrote) {
                        CDB___db_err(dbenv, "%s: unable to flush page: %lu",
                            CDB___memp_fns(dbmp, mfp), (u_long)pgno);
                        return (EPERM);
                }

                ++c_mp->stat.st_page_trickle;
                if (nwrotep != NULL)
                        ++*nwrotep;
                goto loop;
        }

        return (0);
}

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