From f5baac354db8b6abfe8ed4ff6b6c3438c42ea606 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Mon, 12 Aug 2013 20:50:06 +1000 Subject: [PATCH] xfs: avoid CIL allocation during insert Now that we have the size of the log vector that has been allocated, we can determine if we need to allocate a new log vector for formatting and insertion. We only need to allocate a new vector if it won't fit into the existing buffer. However, we need to hold the CIL context lock while we do this so that we can't race with a push draining the currently queued log vectors. It is safe to do this as long as we do GFP_NOFS allocation to avoid avoid memory allocation recursing into the filesystem. Hence we can safely overwrite the existing log vector on the CIL if it is large enough to hold all the dirty regions of the current item. Signed-off-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_log_cil.c | 52 ++++++++++++++++++++++++++++---------------- fs/xfs/xfs_trans.h | 1 - 2 files changed, 33 insertions(+), 20 deletions(-) diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c index 423ceaf0aeb0..b20b15761e9c 100644 --- a/fs/xfs/xfs_log_cil.c +++ b/fs/xfs/xfs_log_cil.c @@ -185,6 +185,22 @@ xlog_cil_prepare_log_vecs( buf_size = sizeof(struct xfs_log_vec) + nbytes + niovecs * sizeof(struct xfs_log_iovec); + /* compare to existing item size */ + if (lip->li_lv && buf_size <= lip->li_lv->lv_size) { + /* same or smaller, optimise common overwrite case */ + lv = lip->li_lv; + lv->lv_next = NULL; + + if (ordered) + goto insert; + + /* Ensure the lv is set up according to ->iop_size */ + lv->lv_niovecs = niovecs; + lv->lv_buf = (char *)lv + buf_size - nbytes; + lv->lv_buf_len = xlog_cil_lv_item_format(lip, lv); + goto insert; + } + /* allocate new data chunk */ lv = kmem_zalloc(buf_size, KM_SLEEP|KM_NOFS); lv->lv_item = lip; @@ -204,8 +220,8 @@ xlog_cil_prepare_log_vecs( lv->lv_buf = (char *)lv + buf_size - nbytes; lv->lv_buf_len = xlog_cil_lv_item_format(lip, lv); - ASSERT(lv->lv_buf_len <= nbytes); insert: + ASSERT(lv->lv_buf_len <= nbytes); if (!ret_lv) ret_lv = lv; else @@ -230,7 +246,17 @@ xfs_cil_prepare_item( { struct xfs_log_vec *old = lv->lv_item->li_lv; - if (old) { + if (!old) { + /* new lv, must pin the log item */ + ASSERT(!lv->lv_item->li_lv); + + if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED) { + *len += lv->lv_buf_len; + *diff_iovecs += lv->lv_niovecs; + } + lv->lv_item->li_ops->iop_pin(lv->lv_item); + + } else if (old != lv) { /* existing lv on log item, space used is a delta */ ASSERT((old->lv_buf && old->lv_buf_len && old->lv_niovecs) || old->lv_buf_len == XFS_LOG_VEC_ORDERED); @@ -249,15 +275,8 @@ xfs_cil_prepare_item( *diff_iovecs += lv->lv_niovecs - old->lv_niovecs; kmem_free(old); } else { - /* new lv, must pin the log item */ - ASSERT(!lv->lv_item->li_lv); - - if (lv->lv_buf_len != XFS_LOG_VEC_ORDERED) { - *len += lv->lv_buf_len; - *diff_iovecs += lv->lv_niovecs; - } - IOP_PIN(lv->lv_item); - + /* re-used lv */ + /* XXX: can't account for len/diff_iovecs yet */ } /* attach new log vector to log item */ @@ -733,18 +752,13 @@ xfs_log_commit_cil( if (flags & XFS_TRANS_RELEASE_LOG_RES) log_flags = XFS_LOG_REL_PERM_RESERV; - /* - * Do all the hard work of formatting items (including memory - * allocation) outside the CIL context lock. This prevents stalling CIL - * pushes when we are low on memory and a transaction commit spends a - * lot of time in memory reclaim. - */ + /* lock out background commit */ + down_read(&log->l_cilp->xc_ctx_lock); + log_vector = xlog_cil_prepare_log_vecs(tp); if (!log_vector) return ENOMEM; - /* lock out background commit */ - down_read(&log->l_cilp->xc_ctx_lock); if (commit_lsn) *commit_lsn = log->l_cilp->xc_ctx->sequence; diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h index 24bbdcd297c7..4786170baeb0 100644 --- a/fs/xfs/xfs_trans.h +++ b/fs/xfs/xfs_trans.h @@ -77,7 +77,6 @@ struct xfs_item_ops { void (*iop_committing)(xfs_log_item_t *, xfs_lsn_t); }; -#define IOP_PIN(ip) (*(ip)->li_ops->iop_pin)(ip) #define IOP_UNPIN(ip, remove) (*(ip)->li_ops->iop_unpin)(ip, remove) #define IOP_PUSH(ip, list) (*(ip)->li_ops->iop_push)(ip, list) #define IOP_UNLOCK(ip) (*(ip)->li_ops->iop_unlock)(ip) -- 2.20.1