xfs: Reduce allocations during CIL insertion

Now that we have the size of the object before the formatting pass
is called, we can allocation the log vector and it's buffer in a
single allocation rather than two separate allocations.

Store the size of the allocated buffer in the log vector so that
we potentially avoid allocation for future modifications of the
object.

While touching this code, remove the IOP_FORMAT definition.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 56 insertions, 39 deletions

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 4e108720a789..423ceaf0aeb0 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -80,6 +80,36 @@ xlog_cil_init_post_recovery(
                                                                 log->l_curr_block);
 }
 
+STATIC int
+xlog_cil_lv_item_format(
+        struct xfs_log_item     *lip,
+        struct xfs_log_vec      *lv)
+{
+        int     index;
+        char    *ptr;
+
+        /* format new vectors into array */
+        lip->li_ops->iop_format(lip, lv->lv_iovecp);
+
+        /* copy data into existing array */
+        ptr = lv->lv_buf;
+        for (index = 0; index < lv->lv_niovecs; index++) {
+                struct xfs_log_iovec *vec = &lv->lv_iovecp[index];
+
+                memcpy(ptr, vec->i_addr, vec->i_len);
+                vec->i_addr = ptr;
+                ptr += vec->i_len;
+        }
+
+        /*
+         * some size calculations for log vectors over-estimate, so the caller
+         * doesn't know the amount of space actually used by the item. Return
+         * the byte count to the caller so they can check and store it
+         * appropriately.
+         */
+        return ptr - lv->lv_buf;
+}
+
 /*
  * Format log item into a flat buffers
  *
@@ -111,7 +141,7 @@ xlog_cil_prepare_log_vecs(
         struct xfs_trans        *tp)
 {
         struct xfs_log_item_desc *lidp;
-        struct xfs_log_vec      *lv = NULL;
+        struct xfs_log_vec      *prev_lv = NULL;
         struct xfs_log_vec      *ret_lv = NULL;
 
 
@@ -123,12 +153,10 @@ xlog_cil_prepare_log_vecs(
 
         list_for_each_entry(lidp, &tp->t_items, lid_trans) {
                 struct xfs_log_item *lip = lidp->lid_item;
-                struct xfs_log_vec *new_lv;
-                void    *ptr;
-                int     index;
-                int     len = 0;
-                uint    niovecs = 0;
-                uint    nbytes = 0;
+                struct xfs_log_vec *lv;
+                int     niovecs = 0;
+                int     nbytes = 0;
+                int     buf_size;
                 bool    ordered = false;
 
                 /* Skip items which aren't dirty in this transaction. */
@@ -150,48 +178,39 @@ xlog_cil_prepare_log_vecs(
                 if (niovecs == XFS_LOG_VEC_ORDERED) {
                         ordered = true;
                         niovecs = 0;
+                        nbytes = 0;
                 }
 
-                new_lv = kmem_zalloc(sizeof(*new_lv) +
-                                niovecs * sizeof(struct xfs_log_iovec),
-                                KM_SLEEP|KM_NOFS);
+                /* calc buffer size */
+                buf_size = sizeof(struct xfs_log_vec) + nbytes +
+                                niovecs * sizeof(struct xfs_log_iovec);
 
-                new_lv->lv_item = lip;
-                new_lv->lv_niovecs = niovecs;
+                /* allocate new data chunk */
+                lv = kmem_zalloc(buf_size, KM_SLEEP|KM_NOFS);
+                lv->lv_item = lip;
+                lv->lv_size = buf_size;
+                lv->lv_niovecs = niovecs;
                 if (ordered) {
                         /* track as an ordered logvec */
-                        new_lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
-                        goto next;
+                        ASSERT(lip->li_lv == NULL);
+                        lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
+                        goto insert;
                 }
 
                 /* The allocated iovec region lies beyond the log vector. */
-                new_lv->lv_iovecp = (struct xfs_log_iovec *)&new_lv[1];
-
-                /* build the vector array and calculate it's length */
-                IOP_FORMAT(new_lv->lv_item, new_lv->lv_iovecp);
-                for (index = 0; index < new_lv->lv_niovecs; index++)
-                        len += new_lv->lv_iovecp[index].i_len;
+                lv->lv_iovecp = (struct xfs_log_iovec *)&lv[1];
 
-                new_lv->lv_buf_len = len;
-                new_lv->lv_buf = kmem_alloc(new_lv->lv_buf_len,
-                                KM_SLEEP|KM_NOFS);
-                ptr = new_lv->lv_buf;
-
-                for (index = 0; index < new_lv->lv_niovecs; index++) {
-                        struct xfs_log_iovec *vec = &new_lv->lv_iovecp[index];
-
-                        memcpy(ptr, vec->i_addr, vec->i_len);
-                        vec->i_addr = ptr;
-                        ptr += vec->i_len;
-                }
-                ASSERT(ptr == new_lv->lv_buf + new_lv->lv_buf_len);
+                /* The allocated data region lies beyond the iovec region */
+                lv->lv_buf = (char *)lv + buf_size - nbytes;
 
-next:
+                lv->lv_buf_len = xlog_cil_lv_item_format(lip, lv);
+                ASSERT(lv->lv_buf_len <= nbytes);
+insert:
                 if (!ret_lv)
-                        ret_lv = new_lv;
+                        ret_lv = lv;
                 else
-                        lv->lv_next = new_lv;
-                lv = new_lv;
+                        prev_lv->lv_next = lv;
+                prev_lv = lv;
         }
 
         return ret_lv;
@@ -228,7 +247,6 @@ xfs_cil_prepare_item(
 
                 *len += lv->lv_buf_len - old->lv_buf_len;
                 *diff_iovecs += lv->lv_niovecs - old->lv_niovecs;
-                kmem_free(old->lv_buf);
                 kmem_free(old);
         } else {
                 /* new lv, must pin the log item */
@@ -354,7 +372,6 @@ xlog_cil_free_logvec(
 
         for (lv = log_vector; lv; ) {
                 struct xfs_log_vec *next = lv->lv_next;
-                kmem_free(lv->lv_buf);
                 kmem_free(lv);
                 lv = next;
         }