From bdb7df42451836f629e725de74b4edbc5e16ff49 Mon Sep 17 00:00:00 2001 From: Alexander Motin Date: Fri, 11 Aug 2023 12:04:08 -0400 Subject: [PATCH] ZIL: Avoid dbuf_read() before dmu_sync(). In most cases dmu_sync() works with dirty records directly and does not need actual data. The only exception is dmu_sync_late_arrival(). To save some CPU time use dmu_buf_hold_noread*() in z*_get_data() and explicitly call dbuf_read() in dmu_sync_late_arrival(). There is also a chance that by that time TXG will already be synced and we won't have to do it at all. Reviewed-by: Brian Atkinson Reviewed-by: Brian Behlendorf Signed-off-by: Alexander Motin Sponsored by: iXsystems, Inc. Closes #15153 --- include/sys/dmu.h | 4 ++++ include/sys/dmu_impl.h | 2 -- module/zfs/dmu.c | 9 ++++++++- module/zfs/zfs_vnops.c | 4 ++-- module/zfs/zvol.c | 4 ++-- 5 files changed, 16 insertions(+), 7 deletions(-) diff --git a/include/sys/dmu.h b/include/sys/dmu.h index a84175c980..1cc8b8971a 100644 --- a/include/sys/dmu.h +++ b/include/sys/dmu.h @@ -572,11 +572,15 @@ int dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset, int dmu_buf_hold_array(objset_t *os, uint64_t object, uint64_t offset, uint64_t length, int read, const void *tag, int *numbufsp, dmu_buf_t ***dbpp); +int dmu_buf_hold_noread(objset_t *os, uint64_t object, uint64_t offset, + const void *tag, dmu_buf_t **dbp); int dmu_buf_hold_by_dnode(dnode_t *dn, uint64_t offset, const void *tag, dmu_buf_t **dbp, int flags); int dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset, uint64_t length, boolean_t read, const void *tag, int *numbufsp, dmu_buf_t ***dbpp, uint32_t flags); +int dmu_buf_hold_noread_by_dnode(dnode_t *dn, uint64_t offset, const void *tag, + dmu_buf_t **dbp); /* * Add a reference to a dmu buffer that has already been held via * dmu_buf_hold() in the current context. diff --git a/include/sys/dmu_impl.h b/include/sys/dmu_impl.h index ce6ae3c665..83ae2b76ba 100644 --- a/include/sys/dmu_impl.h +++ b/include/sys/dmu_impl.h @@ -247,8 +247,6 @@ typedef struct dmu_sendstatus { void dmu_object_zapify(objset_t *, uint64_t, dmu_object_type_t, dmu_tx_t *); void dmu_object_free_zapified(objset_t *, uint64_t, dmu_tx_t *); -int dmu_buf_hold_noread(objset_t *, uint64_t, uint64_t, - const void *, dmu_buf_t **); #ifdef __cplusplus } diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c index c2565b50b7..a63aac51f2 100644 --- a/module/zfs/dmu.c +++ b/module/zfs/dmu.c @@ -165,7 +165,7 @@ dmu_object_byteswap_info_t dmu_ot_byteswap[DMU_BSWAP_NUMFUNCS] = { { zfs_acl_byteswap, "acl" } }; -static int +int dmu_buf_hold_noread_by_dnode(dnode_t *dn, uint64_t offset, const void *tag, dmu_buf_t **dbp) { @@ -185,6 +185,7 @@ dmu_buf_hold_noread_by_dnode(dnode_t *dn, uint64_t offset, *dbp = &db->db; return (0); } + int dmu_buf_hold_noread(objset_t *os, uint64_t object, uint64_t offset, const void *tag, dmu_buf_t **dbp) @@ -1672,6 +1673,12 @@ dmu_sync_late_arrival(zio_t *pio, objset_t *os, dmu_sync_cb_t *done, zgd_t *zgd, { dmu_sync_arg_t *dsa; dmu_tx_t *tx; + int error; + + error = dbuf_read((dmu_buf_impl_t *)zgd->zgd_db, NULL, + DB_RF_CANFAIL | DB_RF_NOPREFETCH); + if (error != 0) + return (error); tx = dmu_tx_create(os); dmu_tx_hold_space(tx, zgd->zgd_db->db_size); diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c index c6831ff6cd..8a3b08139b 100644 --- a/module/zfs/zfs_vnops.c +++ b/module/zfs/zfs_vnops.c @@ -917,8 +917,8 @@ zfs_get_data(void *arg, uint64_t gen, lr_write_t *lr, char *buf, } #endif if (error == 0) - error = dmu_buf_hold(os, object, offset, zgd, &db, - DMU_READ_NO_PREFETCH); + error = dmu_buf_hold_noread(os, object, offset, zgd, + &db); if (error == 0) { blkptr_t *bp = &lr->lr_blkptr; diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c index 547687f07e..bbef53e4e4 100644 --- a/module/zfs/zvol.c +++ b/module/zfs/zvol.c @@ -727,8 +727,8 @@ zvol_get_data(void *arg, uint64_t arg2, lr_write_t *lr, char *buf, offset = P2ALIGN_TYPED(offset, size, uint64_t); zgd->zgd_lr = zfs_rangelock_enter(&zv->zv_rangelock, offset, size, RL_READER); - error = dmu_buf_hold_by_dnode(zv->zv_dn, offset, zgd, &db, - DMU_READ_NO_PREFETCH); + error = dmu_buf_hold_noread_by_dnode(zv->zv_dn, offset, zgd, + &db); if (error == 0) { blkptr_t *bp = &lr->lr_blkptr;