diff options
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 18 | ||||
| -rw-r--r-- | src/backend/storage/smgr/md.c | 21 | ||||
| -rw-r--r-- | src/backend/storage/smgr/smgr.c | 22 | ||||
| -rw-r--r-- | src/include/storage/md.h | 2 | ||||
| -rw-r--r-- | src/include/storage/smgr.h | 2 |
5 files changed, 65 insertions, 0 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index b8680cc8fd4..a19595865af 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -1259,6 +1259,7 @@ StartReadBuffersImpl(ReadBuffersOperation *operation, { int actual_nblocks = *nblocks; int io_buffers_len = 0; + int maxcombine = 0; Assert(*nblocks > 0); Assert(*nblocks <= MAX_IO_COMBINE_LIMIT); @@ -1290,6 +1291,23 @@ StartReadBuffersImpl(ReadBuffersOperation *operation, { /* Extend the readable range to cover this block. */ io_buffers_len++; + + /* + * Check how many blocks we can cover with the same IO. The smgr + * implementation might e.g. be limited due to a segment boundary. + */ + if (i == 0 && actual_nblocks > 1) + { + maxcombine = smgrmaxcombine(operation->smgr, + operation->forknum, + blockNum); + if (unlikely(maxcombine < actual_nblocks)) + { + elog(DEBUG2, "limiting nblocks at %u from %u to %u", + blockNum, actual_nblocks, maxcombine); + actual_nblocks = maxcombine; + } + } } } *nblocks = actual_nblocks; diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c index 6796756358f..cc8a80ee961 100644 --- a/src/backend/storage/smgr/md.c +++ b/src/backend/storage/smgr/md.c @@ -804,6 +804,21 @@ buffers_to_iovec(struct iovec *iov, void **buffers, int nblocks) } /* + * mdmaxcombine() -- Return the maximum number of total blocks that can be + * combined with an IO starting at blocknum. + */ +uint32 +mdmaxcombine(SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum) +{ + BlockNumber segoff; + + segoff = blocknum % ((BlockNumber) RELSEG_SIZE); + + return RELSEG_SIZE - segoff; +} + +/* * mdreadv() -- Read the specified blocks from a relation. */ void @@ -833,6 +848,9 @@ mdreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, RELSEG_SIZE - (blocknum % ((BlockNumber) RELSEG_SIZE))); nblocks_this_segment = Min(nblocks_this_segment, lengthof(iov)); + if (nblocks_this_segment != nblocks) + elog(ERROR, "read crosses segment boundary"); + iovcnt = buffers_to_iovec(iov, buffers, nblocks_this_segment); size_this_segment = nblocks_this_segment * BLCKSZ; transferred_this_segment = 0; @@ -956,6 +974,9 @@ mdwritev(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, RELSEG_SIZE - (blocknum % ((BlockNumber) RELSEG_SIZE))); nblocks_this_segment = Min(nblocks_this_segment, lengthof(iov)); + if (nblocks_this_segment != nblocks) + elog(ERROR, "write crosses segment boundary"); + iovcnt = buffers_to_iovec(iov, (void **) buffers, nblocks_this_segment); size_this_segment = nblocks_this_segment * BLCKSZ; transferred_this_segment = 0; diff --git a/src/backend/storage/smgr/smgr.c b/src/backend/storage/smgr/smgr.c index 7b9fa103eff..925728eb6c1 100644 --- a/src/backend/storage/smgr/smgr.c +++ b/src/backend/storage/smgr/smgr.c @@ -88,6 +88,8 @@ typedef struct f_smgr BlockNumber blocknum, int nblocks, bool skipFsync); bool (*smgr_prefetch) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks); + uint32 (*smgr_maxcombine) (SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum); void (*smgr_readv) (SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, void **buffers, BlockNumber nblocks); @@ -117,6 +119,7 @@ static const f_smgr smgrsw[] = { .smgr_extend = mdextend, .smgr_zeroextend = mdzeroextend, .smgr_prefetch = mdprefetch, + .smgr_maxcombine = mdmaxcombine, .smgr_readv = mdreadv, .smgr_writev = mdwritev, .smgr_writeback = mdwriteback, @@ -589,12 +592,28 @@ smgrprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, } /* + * smgrmaxcombine() - Return the maximum number of total blocks that can be + * combined with an IO starting at blocknum. + * + * The returned value includes the IO for blocknum itself. + */ +uint32 +smgrmaxcombine(SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum) +{ + return smgrsw[reln->smgr_which].smgr_maxcombine(reln, forknum, blocknum); +} + +/* * smgrreadv() -- read a particular block range from a relation into the * supplied buffers. * * This routine is called from the buffer manager in order to * instantiate pages in the shared buffer cache. All storage managers * return pages in the format that POSTGRES expects. + * + * If more than one block is intended to be read, callers need to use + * smgrmaxcombine() to check how many blocks can be combined into one IO. */ void smgrreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, @@ -626,6 +645,9 @@ smgrreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, * skipFsync indicates that the caller will make other provisions to * fsync the relation, so we needn't bother. Temporary relations also * do not require fsync. + * + * If more than one block is intended to be read, callers need to use + * smgrmaxcombine() to check how many blocks can be combined into one IO. */ void smgrwritev(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, diff --git a/src/include/storage/md.h b/src/include/storage/md.h index 620f10abdeb..b72293c79a5 100644 --- a/src/include/storage/md.h +++ b/src/include/storage/md.h @@ -32,6 +32,8 @@ extern void mdzeroextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks, bool skipFsync); extern bool mdprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks); +extern uint32 mdmaxcombine(SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum); extern void mdreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, void **buffers, BlockNumber nblocks); extern void mdwritev(SMgrRelation reln, ForkNumber forknum, diff --git a/src/include/storage/smgr.h b/src/include/storage/smgr.h index e15b20a566a..899d0d681c5 100644 --- a/src/include/storage/smgr.h +++ b/src/include/storage/smgr.h @@ -92,6 +92,8 @@ extern void smgrzeroextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks, bool skipFsync); extern bool smgrprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks); +extern uint32 smgrmaxcombine(SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum); extern void smgrreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, void **buffers, BlockNumber nblocks); |